DC Circuits Lab

aimwellrestElectronics - Devices

Oct 7, 2013 (3 years and 10 months ago)

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DC Circuits Lab
Screen 1: Title Page
ELECTRICITY UNIT OBJECTIVES:
1.To observationally define volts, amperes, & ohms.
2.To demonstrate the proper use of the voltmeter, ammeter, and ohmmeter.
3.To show that the bulb's brightness is proportional to the volts dropped across (measured
across) the bulb.
Equipment: 2 students/group need...
1.a digital VOM
2.a 6 volt lantern battery
3.four test leads
4.four pieces of hook up wire with 1 cm of insulation removed from both ends of each wire.
5.three light bulb sockets, three #40 light bulbs, one #41 light bulb, and one dozen connectors
Screen 2: Series B1
SERIES CIRCUITS USING LIGHT BULBS:
1.In ALL of the following experiments, hook up one test lead to the battery horizontally while
the other test lead is hooked up vertically to the battery. In this manner, the test leads can't
contact each other and short out the battery.
2.Use two red test leads to hook up Bulb B1 to the battery VERY BRIEFLY as the bulb will
burn out. You are hooking up one bulb VERY BRIEFLY to just see how brightly one bulb
glows when hooked up to the battery.
3.Draw a diagram in your notes and record your observations (how bright is the single light
bulb?). Note that the meter is not being used as yet. Note also that this is a closed circuit.
Screen 3: Series B1 (Volts Across B1)
SERIES CIRCUITS USING LIGHT BULBS:
NOTE: the light bulb is NOT screwed in all the way in the following instructions until you are
ready to measure the volts EACH TIME (be quick!!).
1.Set the voltmeter's upper dial on the 30 scale
2.Set the voltmeter's lower dial on the DC Volts scale (red) and turn on the meter.
3.Connect the meter's black probe to the negative terminal on the battery & connect the
meter's red probe to the positive terminal on the battery. Next, screw in the light bulb long
enough to measure the volts.
4.If the probes were switched, was anything different on the voltmeter's reading?
5.Record the voltage.
6.Move the meter's two probes over to the two terminals on Bulb B1 -- screw in the light bulb.
Record the voltage -- then unscrew the light bulb.
7.Did connecting the voltmeter to either the bulb or the battery affect either (did the bulb's
brightness change?)?
8.Did the electricity coming out of the battery have choice in the diagram below when the
meter was hooked up?
9.Hooking up the meter as a VOLTMETER can be described using which word (series or
parallel)?
Screen 4: Series B1+B2
SERIES CIRCUITS USING LIGHT BULBS:
1.Use TWO red test leads and ONE piece of wire to hook up the two light bulbs, B1 & B2, to
the battery as shown below. Note the two bulbs' brightness as compared to the circuit that
just had one bulb hooked up.
2.Take turns unscrewing one light bulb at a time. Note what happens.
3.Does electricity have choice in the circuit below?
4.Draw a diagram of the circuit in your notebook.
Document Created by Charles Peirce - 2002
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Screen 5: Series B1+B2 (Volts Across B1)
SERIES CIRCUITS USING LIGHT BULBS:
1.Set the voltmeter's upper dial on the 30 scale
2.Set the voltmeter's lower dial on the DC Volts scale (red) and turn on the meter.
3.Connect the meter's black probe to the negative terminal on the battery, and then, connect
the meter's red probe to the positive terminal on the battery.
4.If the probes were switched, was anything different on the voltmeter's reading?)
5.Record the voltage.
6.Place the meter's two probes on the two terminals on Bulb B1. (now you may set the
meter's top scale to 3). Record the voltage.
7.Did connecting the voltmeter to either the bulb or the battery affect either (did either bulb's
brightness change as the voltmeter measured volts?)?
8.Did the electricity coming out of the battery have choice in the diagram below when the
meter was hooked up?
9.Hooking up the meter as a VOLTMETER can be described using which word (series or
parallel)?
Screen 6: Series B1+B2 (Volts Across B1+B2)
SERIES CIRCUITS USING LIGHT BULBS:
1.Set the voltmeter's upper dial on the 30 scale
2.Set the voltmeter's lower dial on the DC Volts scale (red) and turn on the meter.
3.Place the meter's two probes on the two terminals on Bulb B2. Record the voltage.
4.Did connecting the voltmeter to either the bulb or the battery affect either bulb (did either
bulb's brightness change as the voltmeter measured volts?)?
5.Did the electricity coming out of the battery have choice in the diagram below when the
meter was hooked up?
6.Hooking up the meter as a VOLTMETER can be described using which word (series or
parallel)?
Screen 7: Series B1+B2+B3
SERIES CIRCUITS USING LIGHT BULBS:
1.Use TWO red test leads and TWO pieces of wire to hook up the three light bulbs, B1 & B2 &
B3, to the battery as shown below.
2.Note the three bulbs' brightness as compared to the circuit that just had two bulbs as
compared to the circuit that just had one bulb.
3.Take turns unscrewing one light bulb at a time. Note what happens.
4.Does electricity have choice in the circuit below?
5.Draw a diagram of the circuit in your notebook.
Screen 8: Series B1+B2+B3 (Volts Across B1)
SERIES CIRCUITS USING LIGHT BULBS:
1.Set the voltmeter's upper dial on the 30 scale
2.Set the voltmeter's lower dial on the DC Volts scale (red) and turn on the meter.
3.Connect the meter's black probe to the negative terminal on the battery, and then, connect
the meter's red probe to the positive terminal on the battery.
4.If the probes were switched, was anything different on the voltmeter's reading?)
5.Record the voltage.
6.Move the meter's two probes over to the two terminals on Bulb B1. Record the voltage.
7.Did connecting the voltmeter to either the bulb or the battery affect either (did either bulb's
brightness change as the voltmeter measured volts?)?
8.Did the electricity coming out of the battery have choice in the diagram below when the
meter was hooked up?
9.Hooking up the meter as a VOLTMETER can be described using which word (series or
parallel)?
Document Created by Charles Peirce - 2002
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Screen 9: Series B1+B2+B3 (Volts Across B2)
SERIES CIRCUITS USING LIGHT BULBS:
1.Set the voltmeter's upper dial on the 30 scale
2.Set the voltmeter's lower dial on the DC Volts scale (red) and turn on the meter.
3.Connect the meter's black probe to the negative terminal on the battery, and then, connect
the meter's red probe to the positive terminal on the battery.
4.If the probes were switched, was anything different on the voltmeter's reading?)
5.Record the voltage.
6.Move the meter's two probes over to the two terminals on Bulb B2. Record the voltage.
7.Did connecting the voltmeter to either the bulb or the battery affect either (did either bulb's
brightness change as the voltmeter measured volts?)?
8.Did the electricity coming out of the battery have choice in the diagram below when the
meter was hooked up?
9.Hooking up the meter as a VOLTMETER can be described using which word (series or
parallel)?
Screen 10: Series B1+B2+B3 (Volts Across B3)
SERIES CIRCUITS USING LIGHT BULBS:
1.Set the voltmeter's upper dial on the 30 scale
2.Set the voltmeter's lower dial on the DC Volts scale (red) and turn on the meter.
3.Connect the meter's black probe to the negative terminal on the battery, and then, connect
the meter's red probe to the positive terminal on the battery.
4.If the probes were switched, was anything different on the voltmeter's reading?)
5.Record the voltage.
6.Move the meter's two probes over to the two terminals on Bulb B3. Record the voltage.
7.Did connecting the voltmeter to either the bulb or the battery affect either (did either bulb's
brightness change as the voltmeter measured volts?)?
8.Did the electricity coming out of the battery have choice in the diagram below when the
meter was hooked up?
9.Hooking up the meter as a VOLTMETER can be described using which word (series or
parallel)?
10.EXTRA CREDIT: while measuring the volts across Bulb B3 below, unscrew Bulb B3.
Explain the results, including the reading on the voltmeter. TOO HARD? Record the page
number. When you are along in the following resistors' experiments, you may get the
explanation.
Screen 11: Series B1+B2+B3 (Short B3)
SERIES CIRCUITS USING LIGHT BULBS:
1.Make sure all three bulbs are glowing in the series circuit below.
2.Connect the two terminals of Bulb B3 together as shown below with one test lead (green
wire in the picture below).
3.Does the electricity at Bulb B3 have choice?
4.Why doesn't the electricity go through the Bulb B3? (...electricity takes the path of least
resistance...because electricity would have to do work if it went through the light bulb...)
5.Set the voltmeter on the 30 scale and DC volts. Measure & record the volts across B3
NOW.
6.What is that green wire called?
7.Did the voltmeter affect the Bulb B3 like that green wire did? Compare the resistance of the
voltmeter with the resistance of the "short".
8.Conclusion? Adding more light bulbs in a series circuit increases what characteristic of that
circuit?
9.What is the resistance of a bulb that has burned out?
10.What is the resistance of an empty socket?
11.What is the mathematical relationship between the bulbs' brightness and volts?
12.Give four operational definitions of a series circuit: answers...
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a.disconnecting one appliance disconnects the rest.
b.voltages are shared according to resistance
c.electricity has NO choice (electricity must go through one appliance before it can get to the
next)
d.no two appliances have both of their terminals attached to each other
Screen 12: Replace B3 with a #41 Bulb
SERIES CIRCUITS USING LIGHT BULBS:
To show you that "...all is not what it appears...":
1.Wire the three Bulb's (#40's) in series and hook up the battery to them (have all 3 bulbs
glowing).
2.Replace Bulb B3 with a #41 bulb. DON'T disconnect the battery.
3.Measure the volts across Bulb B3 (now a #41).
4.While you are still measuring those volts across Bulb B3, unscrew it out of the socket.
What does this experiment tell you about your most important operational definition for a
series circuit?
Screen 13: Ammeter for all three bulbs
SERIES CIRCUITS USING LIGHT BULBS:
Note: Replace Bulb B3 with a #40 light bulb again.
1.Objective: to use the meter as an AMMETER and hook it up properly.
2.WARNING: Failure to read these directions carefully will result in a burned out fuse (it
happens FAST). This experiment uses ONE RED TEST LEAD.
3.To measures amperes, set the meter's top dial at 300 mA and the bottom dial at DCmA
(GOLD scale).
4.Connect the meter's BLACK probe to the negative (-) terminal of the battery.
5.Use that ONE red test lead ONLY to connect the positive (+) terminal of the battery to Bulb
B1.
6.Connect Bulb B1 to B2 with ONE piece of wire.
7.Connect Bulb B2 to B3 with ONE piece of wire.
8. Turn on the meter.
NOW NOTE where terminal ONE is below and ON your EQUIPMENT. Terminal one IS NOT
either end of the red test lead !!!
9.Using the red probe of the meter, TOUCH ONLY terminal #1 FIRST, THEN #2, and FINALLY
#3 in succession noting the brightness of each bulb and the milliamperes registered on the
meter.
10.In this experiment, adding more bulbs by moving from terminals 1 to 2 and then to 3
increased what characteristic of the circuit?
11.In this experiment, adding more bulbs decreased what characteristic of the circuit?
12.What is the mathematical relationship between the resistance in a series circuit and the
current used by that circuit?
13.What is the name of that "law" in answer #12?
14.How is the ammeter hooked up in any circuit?
15.The ammeter can NOT do what to the circuit's resistance?
16.Therefore what is the ammeter's resistance?
17.What piece of "equipment" have you worked with so far that has essentially the same
resistance as the ammeter?
18.Why can't the fuse be burned out on this meter when it acts as a voltmeter even if you
hook it up correctly?
Screen 14: Resistor Color Code
SERIES CIRCUITS USING RESISTANCES:
1.Introducing the Color Code for Resistors:
Since light bulbs have a (+) varying resistance with filament temperature, experiments from
this point on will use resistors. But resistors only tell the user when too much electricity is
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going through them (they'll give off smoke!) -- no light to help you. So we must use a color
code to determine resistance in OHMS (symbol: ￿, pronounced as "omega").
2.The first two colored stripes represent two significant figures and the third stripe indicates
the multiplier (zero's).
3.This is the color code:
First 2 sig. fig.'s multiplier tolerance
black 0 1
brown 1 10
red 2 100
orange 3 1000
yellow 4 10000
green 5 100000
blue 6 1000000
violet 7 10000000
Gray 8 100000000
White 9 1000000000
Gold .1 5%
Silver .01 10%
4.The first three resistors will be identical. Look at the colors on the resistors below. Figure
out their resistance.
5.Set the meter's top dial at 30 and the bottom dial at K￿ (blue for kilohms). Note that there is
NO battery in this picture OR extra wires as the ohmmeter puts out its own electricity to test
the resistors. Measure & record the kilohms ( K￿'s) of each resistor.
6.Place the cursor in each BLUE block below to record the appropriate resistance.
7.Measure R1 & R2 in series.
8.Measure R1 & R2 & R3 in series. Record that value in the BLUE "RT" block below.
Screen 15: Series R1 (LIKE R’s)
SERIES CIRCUITS USING RESISTANCES:
1.In ALL of the following experiments, hook up one test lead to the battery horizontally while
the other test lead is hooked up vertically to the battery. In this manner, the test leads can't
contact each other and short out the battery.
2.The circuits wired will be series circuits. Use only two red test leads.
3.NEVER, ever, directly hook up the AMMETER to the battery (meter set on the gold DCmA).
KEEP at least ONE RESISTOR between the DCmA and the battery or the FUSE will BURN OUT
instantly!!!!
Screen 16: Series R1 (V1)
SERIES CIRCUITS USING RESISTANCES:
1.Set the voltmeter's upper dial on the 30 scale
2.Set the voltmeter's lower dial on the DC Volts scale (red) and turn on the meter.
3.Connect the meter's black probe to the negative terminal on the battery, and then, connect
the meter's red probe to the positive terminal on the battery (does the picture below agree?).
4.If the probes were switched, was anything different on the voltmeter's reading?
5.Record the voltage on the battery.
6.Move the meter's two probes over to the two terminals on R1. Why is the voltage still the
same?
7.Did the electricity coming out of the battery have choice in the diagram below when the
meter was hooked up?
8.Hooking up the meter as a VOLTMETER can be described using which word (series or
parallel)?
Screen 17: Series R1+R2
SERIES CIRCUITS USING RESISTANCES:
1.Use two red test leads and one piece of wire to wire the two resistors in series to the
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battery.
2.How do we know that the resistors are wired in series?
3.Keep in mind: if there is a bad connection, how will you know when there's no bulbs to
"shine" or "tell" you?
Screen 18: R1+R2 (V1+V2)
SERIES CIRCUITS USING RESISTANCES:
1.Set the voltmeter's upper dial on the 30 scale
2.Set the voltmeter's lower dial on the DC Volts scale (red) and turn on the meter.
3.Connect the meter's black probe to the negative terminal on the battery, and then, connect
the meter's red probe to the positive terminal on the battery (does this picture below agree?).
4.If the probes were switched, was anything different on the voltmeter's reading?
5.Record the voltage on the battery.
6.Move the meter's two probes over to the two terminals on R1. Record the voltage as V1.
7.Move the meter's two probes over to the two terminals on R2. Record the voltage as V2.
8.Did the electricity coming out of the battery have choice in the diagram below when the
meter was hooked up?
9.Hooking up the meter as a VOLTMETER can be described using which word (series or
parallel)?
Screen 19: Series R1+R2+R3
SERIES CIRCUITS USING RESISTANCES:
1.Use two red test leads and two pieces of wire to wire the three resistors in series to the
battery.
2.How do we know that the resistors are wired in series?
3.Keep in mind: if there is a bad connection, how will you know when there's no bulbs to
"shine" or "tell" you?
Screen 20: Series R1+R2+R3 (V1+V2+V3)
SERIES CIRCUITS USING RESISTANCES:
1.Set the voltmeter's upper dial on the 30 scale
2.Set the voltmeter's lower dial on the DC Volts scale (red) and turn on the meter.
3.Connect the meter's black probe to the negative terminal on the battery, and then, connect
the meter's red probe to the positive terminal on the battery (does this picture below agree?).
4.If the probes were switched, was anything different on the voltmeter's reading?
5.Record the voltage on the battery.
6.Move the meter's two probes over to the two terminals on R1. Record the voltage as V1.
7.Move the meter's two probes over to the two terminals on R2. Record the voltage as V2.
8.Move the meter's two probes over to the two terminals on R3. Record the voltage as V3.
9.Did the electricity coming out of the battery have choice in the diagram below when the
meter was hooked up?
10.Hooking up the meter as a VOLTMETER can be described using which word (series or
parallel)?
Screen 21: Series Ammeter (R1+R2+R3)
MEASURING CURRENT IN A SERIES CIRCUIT
Note: the statistics that are typed into the light blue box below are for THREE individual
circuits!
1.Objective: to use the meter as an ammeter and hook it up properly.
2.WARNING: Failure to read these directions carefully can result in a burned out fuse (it
happens FAST). This experiment uses ONE RED TEST LEAD.
3.To measures amperes, set the meter's top dial at 300 mA and the bottom dial at DCmA
(GOLD scale).
4.Connect the meter's BLACK probe to the negative (-) terminal of the battery.
5.Use that ONE red test lead ONLY to connect the positive (+) terminal of the battery to R1.
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6.Connect R1 to R2 with ONE piece of wire.
7.Connect R2 to R3 with ONE piece of wire.
8. Turn on the meter.
NOW NOTE where terminal ONE is below and ON your EQUIPMENT. Terminal one IS NOT
either end of the red test lead !!!
9.Using the red probe of the meter, TOUCH ONLY terminal #1 FIRST, THEN #2, and FINALLY
#3 in succession RECORDING the milliamperes registered on the meter in the BLUE boxes
below.
10.DRAW a diagram of this circuit in your notes.
11.In this experiment, adding more R's by moving from terminals 1 to 2 and then to 3
increased what characteristic of the circuit?
12.In this experiment, adding more R's decreased what characteristic of the circuit?
13.What is the mathematical relationship between the RESISTANCE in a series circuit and the
CURRENT used by that circuit?
14.What is the name of that "law" in answer #12?
15.How is the ammeter hooked up in any circuit?
16.The ammeter can NOT do what to the circuit's resistance?
17.Therefore what is the ammeter's resistance?
18.What piece of "equipment" have you worked with so far that has essentially the same
resistance as the ammeter?
19.Why can't the fuse be burned out on this meter when it acts as a voltmeter even if you
hook it up incorrectly?
Screen 22: Series R1 (Unlike R’s)
SERIES CIRCUITS USING UNLIKE RESISTANCES:
1.In ALL of the following experiments, hook up one test lead to the battery horizontally while
the other test lead is hooked up vertically to the battery. In this manner, the test leads can't
contact each other and short out the battery.
2.The circuits wired will be series circuits. Use only two red test leads.
3.NEVER, ever, directly hook up the AMMETER to the battery (meter set on the gold DCmA).
KEEP at least ONE RESISTOR between the DCmA and the battery or the FUSE will BURN OUT
instantly!!!!
Screen 23: Series R1 (V1)
SERIES CIRCUITS USING UNLIKE RESISTANCES:
1.Set the voltmeter's upper dial on the 30 scale
2.Set the voltmeter's lower dial on the DC Volts scale (red) and turn on the meter.
3.Connect the meter's black probe to the negative terminal on the battery, and then, connect
the meter's red probe to the positive terminal on the battery (does the picture below agree?).
4.If the probes were switched, was anything different on the voltmeter's reading?
5.Record the voltage on the battery.
6.Move the meter's two probes over to the two terminals on R1. Why is the voltage still the
same?
7.Did the electricity coming out of the battery have choice in the diagram below when the
meter was hooked up?
8.Hooking up the meter as a VOLTMETER can be described using which word (series or
parallel)?
Screen 24: Series R1 + R2
SERIES CIRCUITS USING UNLIKE RESISTANCES:
1.Use two red test leads and one piece of wire to wire the two resistors in series to the
battery.
2.How do we know that the resistors are wired in series?
3.Keep in mind: if there is a bad connection, how will you know when there's no bulbs to
"shine" or "tell" you?
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Screen 25: Series R1 + R2 (V1 + V2)
SERIES CIRCUITS USING UNLIKE RESISTANCES:
1.Set the voltmeter's upper dial on the 30 scale
2.Set the voltmeter's lower dial on the DC Volts scale (red) and turn on the meter.
3.Connect the meter's black probe to the negative terminal on the battery, and then, connect
the meter's red probe to the positive terminal on the battery (does this picture below agree?).
4.If the probes were switched, was anything different on the voltmeter's reading?
5.Record the voltage on the battery.
6.Move the meter's two probes over to the two terminals on R1. Record the voltage as V1.
7.Move the meter's two probes over to the two terminals on R2. Record the voltage as V2.
8.Did the electricity coming out of the battery have choice in the diagram below when the
meter was hooked up?
9.Hooking up the meter as a VOLTMETER can be described using which word (series or
parallel)?
Screen 26: Series R1 + R2 + R3
SERIES CIRCUITS USING UNLIKE RESISTANCES:
1.Use two red test leads and two pieces of wire to wire the three resistors in series to the
battery.
2.How do we know that the resistors are wired in series?
3.Keep in mind: if there is a bad connection, how will you know when there's no bulbs to
"shine" or "tell" you?
Screen 27: Series R1 + R2 + R3 (V1 + V2 + V3)
SERIES CIRCUITS USING UNLIKE RESISTANCES:
1.Set the voltmeter's upper dial on the 30 scale
2.Set the voltmeter's lower dial on the DC Volts scale (red) and turn on the meter.
3.Connect the meter's black probe to the negative terminal on the battery, and then, connect
the meter's red probe to the positive terminal on the battery (does this picture below agree?).
4.If the probes were switched, was anything different on the voltmeter's reading?
5.Record the voltage on the battery.
6.Move the meter's two probes over to the two terminals on R1. Record the voltage as V1.
7.Move the meter's two probes over to the two terminals on R2. Record the voltage as V2.
8.Move the meter's two probes over to the two terminals on R3. Record the voltage as V3.
9.Did the electricity coming out of the battery have choice in the diagram below when the
meter was hooked up?
10.Hooking up the meter as a VOLTMETER can be described using which word (series or
parallel)?
Screen 28: Series Ammeter (R1 + R2 + R3)
MEASURING CURRENT IN A SERIES CIRCUIT
Note: the statistics that are typed into the light blue box below are for THREE individual
circuits!
1.Objective: to use the meter as an ammeter and hook it up properly.
2.WARNING: Failure to read these directions carefully can result in a burned out fuse (it
happens FAST). This experiment uses ONE RED TEST LEAD.
3.To measures amperes, set the meter's top dial at 300 mA and the bottom dial at DCmA
(GOLD scale).
4.Connect the meter's BLACK probe to the negative (-) terminal of the battery.
5.Use that ONE red test lead ONLY to connect the positive (+) terminal of the battery to R1.
6.Connect R1 to R2 with ONE piece of wire.
7.Connect R2 to R3 with ONE piece of wire.
8. Turn on the meter.
NOW NOTE where terminal ONE is below and ON your EQUIPMENT. Terminal one IS NOT
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either end of the red test lead !!!
9.Using the red probe of the meter, TOUCH ONLY terminal #1 FIRST, THEN #2, and FINALLY
#3 in succession RECORDING the milliamperes registered on the meter in the BLUE boxes
below.
9.DRAW a diagram of this circuit in your notes.
10.In this experiment, adding more R's by moving from terminals 1 to 2 and then to 3
increased what characteristic of the circuit?
11.In this experiment, adding more R's decreased what characteristic of the circuit?
12.What is the mathematical relationship between the RESISTANCE in a series circuit and the
CURRENT used by that circuit?
13.What is the name of that "law" in answer #12?
14.How is the ammeter hooked up in any circuit?
15.The ammeter can NOT do what to the circuit's resistance?
16.Therefore what is the ammeter's resistance?
17.What piece of "equipment" have you worked with so far that has essentially the same
resistance as the ammeter?
18.Why can't the fuse be burned out on this meter when it acts as a voltmeter even if you
hook it up incorrectly?
Screen 29: Series Circuit Analysis
Note: the statistics that are typed into the YELLOW, GRAY, & WHITE boxes ABOVE are for
ONE series circuit containing THREE resistors.
The student should have a diagram of the circuit in the upper left corner of this page
LABELED in his/her notebook BEFORE attempting to fill in the ABOVE chart.
1.Analysis Chart: Type in the ￿'s (ohms) for resistors R1, R2, & R3 in the yellow blocks of the
chart.
2.There are two ways to calculate the voltages in a series circuit. BOTH ways should be
checked with a calculator, then type in the numbers in the gray blocks in the chart.
3.One method uses a proportion called the voltage divider formula: volts are divided up in a
series circuit according to the resistance of the resistors. That is, the highest resistor gets
the highest volts; the lowest resistor gets the lowest volts. Notice that the SUBSCRIPTS are
the same in both numerators & the same in both denominators.
4.The other voltage method uses Ohm's Law, V=IR .Notice that the SUBSCRIPTS are the
same in the formula.
5.Current is calcuated as I=V/R for each resistor (the white box below). Note that the
answers in the white blocks should be the same.
To summarize: series circuits use these formulas:
6. VT = V1 + V2 + V3 + (etc.) (volts are shared according to R's)
7. RT = R1 + R2 + R3 + (etc.) (resistance adds up in a series circuit)
8. IT = I1 = I2 = I3 + (etc.) (those i's are equal in the formula)
Screen 30: Series R1 (Unlike R’s)
SERIES CIRCUITS USING UNLIKE RESISTANCES:
1.In ALL of the following experiments, hook up one test lead to the battery horizontally while
the other test lead is hooked up vertically to the battery. In this manner, the test leads can't
contact each other and short out the battery.
2.The circuits wired will be series circuits. Use only two red test leads.
3.NEVER, ever, directly hook up the AMMETER to the battery (meter set on the gold DCmA).
KEEP at least ONE RESISTOR between the DCmA and the battery or the FUSE will BURN OUT
instantly!!!!
Screen 31: Series R1 (V1)
SERIES CIRCUITS USING UNLIKE RESISTANCES:
1.Set the voltmeter's upper dial on the 30 scale
2.Set the voltmeter's lower dial on the DC Volts scale (red) and turn on the meter.
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3.Connect the meter's black probe to the negative terminal on the battery, and then, connect
the meter's red probe to the positive terminal on the battery (does the picture below agree?).
4.If the probes were switched, was anything different on the voltmeter's reading?
5.Record the voltage on the battery.
6.Move the meter's two probes over to the two terminals on R1. Why is the voltage still the
same?
7.Did the electricity coming out of the battery have choice in the diagram below when the
meter was hooked up?
8.Hooking up the meter as a VOLTMETER can be described using which word (series or
parallel)?
Screen 32: Series R1 + R2
SERIES CIRCUITS USING UNLIKE RESISTANCES:
1.Use two red test leads and one piece of wire to wire the two resistors in series to the
battery.
2.How do we know that the resistors are wired in series?
3.Keep in mind: if there is a bad connection, how will you know when there's no bulbs to
"shine" or "tell" you?
Screen 33: Series R1 + R2 (V1 + V2)
SERIES CIRCUITS USING UNLIKE RESISTANCES:
1.Set the voltmeter's upper dial on the 30 scale
2.Set the voltmeter's lower dial on the DC Volts scale (red) and turn on the meter.
3.Connect the meter's black probe to the negative terminal on the battery, and then, connect
the meter's red probe to the positive terminal on the battery (does this picture below agree?).
4.If the probes were switched, was anything different on the voltmeter's reading?
5.Record the voltage on the battery.
6.Move the meter's two probes over to the two terminals on R1. Record the voltage as V1.
7.Move the meter's two probes over to the two terminals on R2. Record the voltage as V2.
8.Did the electricity coming out of the battery have choice in the diagram below when the
meter was hooked up?
9.Hooking up the meter as a VOLTMETER can be described using which word (series or
parallel)?
Screen 34: Series R1 + R2 + R3
SERIES CIRCUITS USING UNLIKE RESISTANCES:
1.Use two red test leads and two pieces of wire to wire the three resistors in series to the
battery.
2.How do we know that the resistors are wired in series?
3.Keep in mind: if there is a bad connection, how will you know when there's no bulbs to
"shine" or "tell" you?
Screen 35: Series R1 + R2 + R3 (V1 + V2 + V3)
SERIES CIRCUITS USING UNLIKE RESISTANCES:
1.Set the voltmeter's upper dial on the 30 scale
2.Set the voltmeter's lower dial on the DC Volts scale (red) and turn on the meter.
3.Connect the meter's black probe to the negative terminal on the battery, and then, connect
the meter's red probe to the positive terminal on the battery (does this picture below agree?).
4.If the probes were switched, was anything different on the voltmeter's reading?
5.Record the voltage on the battery.
6.Move the meter's two probes over to the two terminals on R1. Record the voltage as V1.
7.Move the meter's two probes over to the two terminals on R2. Record the voltage as V2.
8.Move the meter's two probes over to the two terminals on R3. Record the voltage as V3.
9.Did the electricity coming out of the battery have choice in the diagram below when the
meter was hooked up?
Document Created by Charles Peirce - 2002
Page 10 of 22
10.Hooking up the meter as a VOLTMETER can be described using which word (series or
parallel)?
Screen 36: Series Ammeter (R1 + R2 + R3)
MEASURING CURRENT IN A SERIES CIRCUIT
Note: the statistics that are typed into the light blue box below are for THREE individual
circuits!
1.Objective: to use the meter as an ammeter and hook it up properly.
2.WARNING: Failure to read these directions carefully can result in a burned out fuse (it
happens FAST). This experiment uses ONE RED TEST LEAD.
3.To measures amperes, set the meter's top dial at 300 mA and the bottom dial at DCmA
(GOLD scale).
4.Connect the meter's BLACK probe to the negative (-) terminal of the battery.
5.Use that ONE red test lead ONLY to connect the positive (+) terminal of the battery to R1.
6.Connect R1 to R2 with ONE piece of wire.
7.Connect R2 to R3 with ONE piece of wire.
8. Turn on the meter.
NOW NOTE where terminal ONE is below and ON your EQUIPMENT. Terminal one IS NOT
either end of the red test lead !!!
9.Using the red probe of the meter, TOUCH ONLY terminal #1 FIRST, THEN #2, and FINALLY
#3 in succession RECORDING the milliamperes registered on the meter in the BLUE boxes
below.
9a.DRAW a diagram of this circuit in your notes.
10.In this experiment, adding more R's by moving from terminals 1 to 2 and then to 3
increased what characteristic of the circuit?
11.In this experiment, adding more R's decreased what characteristic of the circuit?
12.What is the mathematical relationship between the RESISTANCE in a series circuit and the
CURRENT used by that circuit?
13.What is the name of that "law" in answer #12?
14.How is the ammeter hooked up in any circuit?
15.The ammeter can NOT do what to the circuit's resistance?
16.Therefore what is the ammeter's resistance?
17.What piece of "equipment" have you worked with so far that has essentially the same
resistance as the ammeter?
18.Why can't the fuse be burned out on this meter when it acts as a voltmeter even if you
hook it up incorrectly?
Screen 37: Series Circuit Analysis
Note: the statistics that are typed into the YELLOW, GRAY, & WHITE boxes ABOVE are for
ONE series circuit containing THREE resistors. The student should have a diagram of the
circuit in the upper left corner of this page LABELED in his/her notebook BEFORE attempting
to fill in the ABOVE chart.
1.Analysis Chart: Type in the ￿'s (ohms) for resistors R1, R2, & R3 in the yellow blocks of the
chart.
2.There are two ways to calculate the voltages in a series circuit. BOTH ways should be
checked with a calculator, then type in the numbers in the gray blocks in the chart.
3.One method uses a proportion called the voltage divider formula: volts are divided up in a
series circuit according to the resistance of the resistors. That is, the highest resistor gets
the highest volts; the lowest resistor gets the lowest volts. Notice that the SUBSCRIPTS are
the same in both numerators & the same in both denominators.
4.The other voltage method uses Ohm's Law, V=IR .Notice that the SUBSCRIPTS are the
same in the formula.
5.Current is calcuated as I=V/R for each resistor (the white box below). Note that the
answers in the white blocks should be the same.
To summarize: series circuits use these formulas:
Document Created by Charles Peirce - 2002
Page 11 of 22
6. VT = V1 + V2 + V3 + (etc.) (volts are shared according to R's)
7. RT = R1 + R2 + R3 + (etc.) (resistance adds up in a series circuit)
8. IT = I1 = I2 = I3 = (etc.) (those i's are equal in the formula)
Screen 38: Parallel Resistance R1 (Exp #1)
PARALLEL CIRCUITS USING UNLIKE RESISTANCES:
1.Set the meter's top dial at 3 and the bottom dial at K￿ (blue for kilohms). Note that there is
NO battery in this picture OR extra wires as the ohmmeter puts out its own electricity to test
the resistors.
2.Place the cursor in each BLUE block below to record the appropriate resistance.
3.Measure R1.
4.Notice that the formula BELOW is called a RECIPROCAL formula. That is, the resistance
value is divided INTO the number 1.
Yes. At this point it does look like a series circuit until the next circuit.
Screen 39: Parallel Resistance R1 + R2
PARALLEL CIRCUITS USING UNLIKE RESISTANCES:
1.Set the meter's top dial at 3 and the bottom dial at K￿ (blue for kilohms). Note that there is
NO battery in this picture OR extra wires as the ohmmeter puts out its own electricity to test
the resistors.
2.Place the cursor in each BLUE block below to record the resistance as OHMS (￿), not as
Kilo￿.
3.Measure R1 & R2 in parallel.
4.Rt in a parallel circuit should ALWAYS be smaller than the smallest R.
5.Notice that the formula BELOW is called a RECIPROCAL formula. That is, the the resistance
value is divided INTO the number 1.
6.After ADDING the reciprocals (decimals), the decimal answer is divided INTO one AGAIN to
calculate the total resistance, RT. Why? Because the original formula has RT in the
denominator. Can your group rewrite the formula so that RT is in the NUMERATOR?
Screen 40: Parallel Resistance R1 + R2 + R3
PARALLEL CIRCUITS USING UNLIKE RESISTANCES:
1.Set the meter's top dial at 3 and the bottom dial at K￿ (blue for kilohms). Note that there is
NO battery in this picture OR extra wires as the ohmmeter puts out its own electricity to test
the resistors.
2.Place the cursor in each BLUE block below to record the resistance as OHMS (￿) , not as
Kilo￿.
3.Measure R1 & R2 & R3 in parallel.
4.RT in a parallel circuit should ALWAYS be smaller than the smallest R.
5.Notice that the formula BELOW is called a RECIPROCAL formula. That is, the the resistance
value is divided INTO the number 1.
6.After ADDING the reciprocals (decimals), the decimal answer is divided INTO one AGAIN to
calculate the total resistance, RT. Why? Because the original formula has RT in the
denominator. Can your group rewrite the formula so that RT is in the NUMERATOR?
Screen 41: Parallel R1
PARALLEL CIRCUITS USING UNLIKE RESISTANCES:
1.Wire the resistor R1 to the battery as shown below.
2.Then go to the next page.
Screen 42: Parallel R1 (V1)
PARALLEL CIRCUITS USING UNLIKE RESISTANCES:
1.Set the voltmeter's upper dial on the 30 scale
2.Set the voltmeter's lower dial on the DC Volts scale (red) and turn on the meter.
3.Connect the meter's black probe to the negative terminal on the battery, and then, connect
Document Created by Charles Peirce - 2002
Page 12 of 22
the meter's red probe to the positive terminal on the battery (does the picture below agree?).
4.If the probes were switched, was anything different on the voltmeter's reading?
5.Record the voltage on the battery.
6.Move the meter's two probes over to the two terminals on R1. Why is the voltage still the
same?
7.Did the electricity coming out of the battery have choice in the diagram below when the
meter was hooked up?
8.Hooking up the meter as a VOLTMETER can be described using which word (series or
parallel)?
Screen 43: Parallel R1 + R2
PARALLEL CIRCUITS USING UNLIKE RESISTANCES:
1.Wire the resistors R1 and R2 to the battery as shown below.
2.Go to the next page.
Screen 44: Parallel R1 + R2 (V1 + V2)
PARALLEL CIRCUITS USING UNLIKE RESISTANCES:
1.Set the voltmeter's upper dial on the 30 scale
2.Set the voltmeter's lower dial on the DC Volts scale (red) and turn on the meter.
3.Connect the meter's black probe to the negative terminal on the battery, and then, connect
the meter's red probe to the positive terminal on the battery (does this picture below agree?).
4.If the probes were switched, was anything different on the voltmeter's reading?
5.Record the voltage on the battery.
6.Move the meter's two probes over to the two terminals on R1. Record the voltage as V1.
7.Move the meter's two probes over to the two terminals on R2. Record the voltage as V2.
8.Did the electricity coming out of the battery have choice in the diagram below when the
meter was hooked up?
9.Hooking up the meter as a VOLTMETER can be described using which word (series or
parallel)?
10.Is there a common sense statement that your group can state that explains why these
voltages are equal so far?
Screen 45: Parallel R1 + R2 + R3
PARALLEL CIRCUITS USING UNLIKE RESISTANCES:
1.Wire the resistors R1, R2, and R3 to the battery as shown below.
2.Go to the next page.
Screen 46: Parallel R1 + R2 + R3 (V1 + V2 + V3)
PARALLEL CIRCUITS USING UNLIKE RESISTANCES:
1.Set the voltmeter's upper dial on the 30 scale
2.Set the voltmeter's lower dial on the DC Volts scale (red) and turn on the meter.
3.Connect the meter's black probe to the negative terminal on the battery, and then, connect
the meter's red probe to the positive terminal on the battery (does this picture below agree?).
4.If the probes were switched, was anything different on the voltmeter's reading?
5.Record the voltage on the battery.
6.Move the meter's two probes over to the two terminals on R1. Record the voltage as V1.
7.Move the meter's two probes over to the two terminals on R2. Record the voltage as V2.
8.Move the meter's two probes over to the two terminals on R3. Record the voltage as V3.
9.Did the electricity coming out of the battery have choice in the diagram below when the
meter was hooked up?
10.Hooking up the meter as a VOLTMETER can be described using which word (series o
equal?
Screen 47: Parallel Ammeter (R1 + R2 + R3)
MEASURING CURRENT IN A PARALLEL CIRCUIT
Document Created by Charles Peirce - 2002
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Note: the statistics that are typed into the light blue box below are for THREE individual
circuits!
1.Objective: to use the meter as an ammeter and hook it up properly.
2.WARNING: Failure to read these directions carefully can result in a burned out fuse (it
happens FAST). This experiment uses ONE RED TEST LEAD.
3.To measures amperes, set the meter's top dial at 300 mA and the bottom dial at DCmA
(GOLD scale).
4.Connect the meter's BLACK probe to the negative (-) terminal of the battery.
5.Use that ONE red test lead ONLY to connect the positive (+) terminal of the battery to R1.
6.Do not connect wire "a" to terminal 2.
7.Do not connect wire "b" to terminal 3.
8. Turn on the meter.
NOW NOTE where terminal ONE is below and ON your EQUIPMENT. Terminal one IS NOT
either end of the red test lead !!!
9.Using the red probe of the meter, TOUCH ONLY terminal #1 FIRST, THEN connect "a" to
terminal 2, and FINALLY connect "b" to terminal "b" in succession RECORDING the
milliamperes registered on the meter in the BLUE boxes below.
9a.DRAW a diagram of this circuit in your notes.
10.In this experiment, adding more R's by moving from terminals 1 to 2 and then to 3
increased what characteristic of the circuit? Compare your answer with question #10 on pp.
28 & 36 (series circuits).
11.In this experiment, adding more R's decreased what characteristic of the circuit? Compare
your answer with question #11 on pp. 28 & 36 (series circuits).
12.What is the mathematical relationship between the RESISTANCE in a PARALLEL circuit and
the CURRENT used by that circuit?
13.What is the name of that "law" in answer #12?
14.How is the ammeter hooked up in any circuit?
15.The ammeter can NOT do what to the circuit's resistance?
16.Therefore what is the ammeter's resistance?
17.What piece of "equipment" have you worked with so far that has essentially the same
resistance as the ammeter?
18.Why can't the fuse be burned out on this meter when it acts as a voltmeter even if you
hook it up incorrectly?
Screen 48: Parallel Circuit Analysis
Note: the statistics that are typed into the YELLOW, GRAY, & WHITE boxes ABOVE are for
ONE parallel circuit containing THREE resistors. The student should have a diagram of the
circuit in the upper left corner of this page LABELED in his/her notebook BEFORE attempting
to fill in the ABOVE chart.
1.Analysis Chart: Type in the ￿'s (ohms) for resistors R1, R2, & R3 in the yellow blocks of the
chart.
2.There are two ways to calculate the resistance in a parallel circuit. BOTH ways should be
checked with a calculator, then type in the numbers in the gray blocks in the chart.
3.
4.The other voltage method uses Ohm's Law, V=IR .Notice that the SUBSCRIPTS are the
same in the formula.
5.Current is calcuated as I=V/R for each resistor (the white box below). Note that the
answers in the white blocks should be the same.
To summarize: parallel circuits use these formulas:
6. VT = V1 = V2 = V3 = (etc.) (volts are shared according to R's)
7. 1/RT = 1/R1 + 1/R2 + 1/R3 + (etc.) (resistance decreases in a parallel circuit as resistors
are "aded")
8. IT = I1 + I2 + I3 + (etc.) (those i's are equal in the formula)
Screen 49: Deriving Reciprocal Resistance Formula
Document Created by Charles Peirce - 2002
Page 14 of 22
DERIVING PARALLEL CIRCUIT'S RECIPROCAL RESISTANCE FORMULA:
Total Current (IT) in a parallel circuit is calculated with the formula...
1. IT = I1 + I2 + I3
so substituting V/R for each I
changes formula #1 to------> 2. VT/RT = V1/R1 + V2/R2 + V3/R3
but VT = V1 = V2 = V3 in a
parallel circuit so that the
numerators cancel out for---> 3. 1/RT = 1/R1 + 1/R2 + 1/R3
Now, check the lab. data----> 4. 1/RT = 1/150 + 1/330 +1/470
to see if -----------------------> 5. RT = 85 ￿
With algebra, the formula is -----> 6. RT=1/(1/R1 + 1/R2 + 1/R3)
obtained and formula #6 is called the
RECIPROCAL of the SUM of the RECIPROCALS.
If the R's are identical (Ri's),
formula #6 becomes -------------> 7. RT = Ri/# of Ri's
If the R's are analyzed in pairs, then RT =(R1 X R2)/(R1 + R2) or
RT becomes easier to verbalize as RT = (product)/(sum)
Your group should ask the teacher to explain this derivation at the chalk board so as to avoid
using slash marks "/".
Note: the RECIPROCAL of resistance is called CONDUCTANCE (G) so that formula #3 above
can be rewritten as GT = G1 + G2 + G3
How important is the above note? Your calculator has a button labeled "1/x" to do reciprocals
automatically for you.
Screen 50: Parallel Resistance R1 (Exp#2)
PARALLEL CIRCUITS USING UNLIKE RESISTANCES:
1.Set the meter's top dial at 30 and the bottom dial at K￿ (blue for kilohms). Note that there is
NO battery in this picture OR extra wires as the ohmmeter puts out its own electricity to test
the resistors.
2.Place the cursor in each BLUE block below to record the appropriate resistance.
3.Measure RT (in this case RT = R1). The ￿'s of RT will also be recorded on pp. 59 & 60
4.Notice that the formula BELOW is called a RECIPROCAL formula. That is, the resistance
value is divided INTO the number 1.
Yes. At this point it does look like a series circuit until the next circuit.
Screen 51: Parallel Resistance R1 + R2
PARALLEL CIRCUITS USING UNLIKE RESISTANCES:
1.Set the meter's top dial at 30 and the bottom dial at K￿ (blue for kilohms). Note that there is
NO battery in this picture OR extra wires as the ohmmeter puts out its own electricity to test
the resistors.
2.Place the cursor in each BLUE block below to record the resistance as OHMS (￿), not as
Kilo￿.
3.Measure R1 & R2 in parallel (in this case RT ≠ R1 + R2). The ￿'s of RT will also be recorded
on pp. 59 & 60
4.RT in a parallel circuit should ALWAYS be smaller than the smallest R.
5.Notice that the formula BELOW is called a RECIPROCAL formula. That is, the the resistance
value is divided INTO the number 1.
6.After ADDING the reciprocals (decimals), the decimal answer is divided INTO one AGAIN to
calculate the total resistance, RT. Why? Because the original formula has RT in the
denominator. Can your group rewrite the formula so that RT is in the NUMERATOR?
Screen 52: Parallel Resistance R1 + R2 + R3
PARALLEL CIRCUITS USING UNLIKE RESISTANCES:
1.Set the meter's top dial at 30 and the bottom dial at K￿ (blue for kilohms). Note that there is
NO battery in this picture OR extra wires as the ohmmeter puts out its own electricity to test
Document Created by Charles Peirce - 2002
Page 15 of 22
the resistors.
2.Place the cursor in each BLUE block below to record the resistance as OHMS (￿) , not as
Kilo￿.
3.Measure R1 & R2 & R3 in parallel (in this case RT ≠ R1 + R2 + R3). The ￿'s of RT will also
be recorded on pp. 59 & 60
4.RT in a parallel circuit should ALWAYS be smaller than the smallest R.
5.Notice that the formula BELOW is called a RECIPROCAL formula. That is, the the resistance
value is divided INTO the number 1.
6.After ADDING the reciprocals (decimals), the decimal answer is divided INTO one AGAIN to
calculate the total resistance, RT. Why? Because the original formula has RT in the
denominator. Can your group rewrite the formula so that RT is in the NUMERATOR?
Screen 53: Parallel R1
PARALLEL CIRCUITS USING UNLIKE RESISTANCES:
1.Wire the resistor R1 to the battery as shown below.
2.Then go to the next page.
Screen 54: Parallel R1 (V1)
PARALLEL CIRCUITS USING UNLIKE RESISTANCES:
1.Set the voltmeter's upper dial on the 30 scale
2.Set the voltmeter's lower dial on the DC Volts scale (red) and turn on the meter.
3.Connect the meter's black probe to the negative terminal on the battery, and then, connect
the meter's red probe to the positive terminal on the battery (does the picture below agree?).
4.If the probes were switched, was anything different on the voltmeter's reading?
5.Record the voltage on the battery.
6.Move the meter's two probes over to the two terminals on R1. Why is the voltage still the
same?
7.Did the electricity coming out of the battery have choice in the diagram below when the
meter was hooked up?
8.Hooking up the meter as a VOLTMETER can be described using which word (series or
parallel)?
Screen 55: Parallel R1 + R2
PARALLEL CIRCUITS USING UNLIKE RESISTANCES:
1.Wire the resistors R1 and R2 to the battery as shown below.
2.Go to the next page.
Screen 56: Parallel R1 + R2 (V1 + V2)
PARALLEL CIRCUITS USING UNLIKE RESISTANCES:
1.Set the voltmeter's upper dial on the 30 scale
2.Set the voltmeter's lower dial on the DC Volts scale (red) and turn on the meter.
3.Connect the meter's black probe to the negative terminal on the battery, and then, connect
the meter's red probe to the positive terminal on the battery (does this picture below agree?).
4.If the probes were switched, was anything different on the voltmeter's reading?
5.Record the voltage on the battery.
6.Move the meter's two probes over to the two terminals on R1. Record the voltage as V1.
7.Move the meter's two probes over to the two terminals on R2. Record the voltage as V2.
8.Did the electricity coming out of the battery have choice in the diagram below when the
meter was hooked up?
9.Hooking up the meter as a VOLTMETER can be described using which word (series or
parallel)?
10.Is there a common sense statement that your group can state that explains why these
voltages are equal so far?
Screen 57: Parallel R1 + R2 + R3
Document Created by Charles Peirce - 2002
Page 16 of 22
PARALLEL CIRCUITS USING UNLIKE RESISTANCES:
1.Wire the resistors R1, R2, and R3 to the battery as shown below.
2.Go to the next page.
Screen 58: Parallel R1 + R2 + R3 (V1 + V2 + V3)
PARALLEL CIRCUITS USING UNLIKE RESISTANCES:
1.Set the voltmeter's upper dial on the 30 scale
2.Set the voltmeter's lower dial on the DC Volts scale (red) and turn on the meter.
3.Connect the meter's black probe to the negative terminal on the battery, and then, connect
the meter's red probe to the positive terminal on the battery (does this picture below agree?).
4.If the probes were switched, was anything different on the voltmeter's reading?
5.Record the voltage on the battery.
6.Move the meter's two probes over to the two terminals on R1. Record the voltage as V1.
7.Move the meter's two probes over to the two terminals on R2. Record the voltage as V2.
8.Move the meter's two probes over to the two terminals on R3. Record the voltage as V3.
9.Did the electricity coming out of the battery have choice in the diagram below when the
meter was hooked up?
10.Hooking up the meter as a VOLTMETER can be described using which word (series or
parallel)?
11.Is there a common sense statement that your group can state that explains why these
voltages are still equal?
Screen 59: Parallel Ammeter (R1 + R2 + R3)
MEASURING CURRENT IN A PARALLEL CIRCUIT
Note: the statistics that are typed into the light blue box below are for THREE individual
circuits!
1.Objective: to use the meter as an ammeter and hook it up properly.
2.WARNING: Failure to read these directions carefully can result in a burned out fuse (it
happens FAST). This experiment uses ONE RED TEST LEAD.
3.To measures amperes, set the meter's top dial at 300 mA and the bottom dial at DCmA
(GOLD scale).
4.Connect the meter's BLACK probe to the negative (-) terminal of the battery.
5.Use that ONE red test lead ONLY to connect the positive (+) terminal of the battery to R1.
6.Do not connect wire "a" to terminal 2.
7.Do not connect wire "b" to terminal 3.
8. Turn on the meter.
NOW NOTE where terminal ONE is below and ON your EQUIPMENT. Terminal one IS NOT
either end of the red test lead !!!
9.Using the red probe of the meter, TOUCH ONLY terminal #1 FIRST, THEN connect "a" to
terminal 2, and FINALLY connect "b" to terminal "b" in succession RECORDING the
milliamperes registered on the meter in the BLUE boxes below.
10.DRAW a diagram of this circuit in your notes.
11.In this experiment, adding more R's by moving from terminals 1 to 2 and then to 3
increased what characteristic of the circuit? Compare your answer with question #10 on pp.
28 & 36 (series circuits).
12.In this experiment, adding more R's decreased what characteristic of the circuit? Compare
your answer with question #11 on pp. 28 & 36 (series circuits).
13.What is the mathematical relationship between the RESISTANCE in a PARALLEL circuit and
the CURRENT used by that circuit?
14.What is the name of that "law" in answer #13?
15.How is the ammeter hooked up in any circuit?
16.The ammeter can NOT do what to the circuit's resistance?
17.Therefore what is the ammeter's resistance?
18.What piece of "equipment" have you worked with so far that has essentially the same
resistance as the ammeter?
Document Created by Charles Peirce - 2002
Page 17 of 22
19.Why can't the fuse be burned out on this meter when it acts as a voltmeter even if you
hook it up incorrectly?
Screen 60: Parallel Circuit Analysis
Note: the statistics that are typed into the YELLOW, GRAY, & WHITE boxes ABOVE are for
ONE parallel circuit containing THREE resistors. The student should have a diagram of the
circuit in the upper left corner of this page LABELED in his/her notebook BEFORE attempting
to fill in the ABOVE chart.
1.Analysis Chart: Type in the ￿'s (ohms) for resistors R1, R2, & R3 in the yellow blocks of the
chart.
2.There are two ways to calculate the resistance in a parallel circuit. BOTH ways should be
checked with a calculator, then type in the numbers in the gray blocks in the chart.
3.
4.The other voltage method uses Ohm's Law, V=IR .Notice that the SUBSCRIPTS are the
same in the formula.
5.Current is calcuated as I=V/R for each resistor (the white box below). Note that the
answers in the white blocks should be the same.
To summarize: parallel circuits use these formulas:
6. VT = V1 = V2 = V3 = (etc.) (volts are shared according to R's)
7. 1/RT = 1/R1 + 1/R2 + 1/R3 + (etc.) (resistance decreases in a parallel circuit as resistors
are "aded")
8. IT = I1 + I2 + I3 + (etc.) (those I's are equal in the formula)
Screen 61: Series/Parallel R1 (Exp#1)
COMBINATION SERIES/PARALLEL CIRCUITS:
1.Set the meter's top dial at 30 and the bottom dial at K￿ (blue for kilohms). Note that there is
NO battery in this picture OR extra wires as the ohmmeter puts out its own electricity to test
the resistors.
2.Place the cursor in each BLUE block below to record the appropriate resistance.
3.Position the circuit board in front of you as shown in the picture. Measure Rt (put the
probes at terminals a and b).
4.Notice that PART OF the formula BELOW is called a RECIPROCAL formula. That is, the
resistance value is divided INTO the number 1 for the resistors wired in parallel.
Screen 62: Series/Parallel R1 (Exp#1)
COMBINATION SERIES/PARALLEL CIRCUITS:
1.Set the meter's top dial at 30 and the bottom dial at K￿ (blue for kilohms). Note that there is
NO battery in this picture OR extra wires as the ohmmeter puts out its own electricity to test
the resistors.
2.Place the cursor in each BLUE block below to record the appropriate resistance.
3.Position the circuit board in front of you as shown in the picture. Measure R23 (put the
probes at terminals b and e).
4.Notice that PART OF the formula BELOW is called a RECIPROCAL formula. That is, the
resistance value is divided INTO the number 1 for the resistors wired in parallel.
Screen 63: Series/Parallel + battery
COMBINATION SERIES/PARALLEL CIRCUITS:
1.Wire the resistors R1, R2, and R3 to the battery as shown below.
2.Then go to the next page.
Screen 64: Series/Parallel (V1)
COMBINATION SERIES/PARALLEL CIRCUITS:
1.Set the voltmeter's upper dial on the 30 scale
2.Set the voltmeter's lower dial on the DC Volts scale (red) and turn on the meter.
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3.Connect the meter's black probe to the negative terminal on the battery, and then, connect
the meter's red probe to the positive terminal on the battery (does this picture below agree?).
4.If the probes were switched, was anything different on the voltmeter's reading?
5.Record the voltage on the battery.
6.Move the meter's two probes over to the two terminals on R1. Record the voltage as V1.
7.Move the meter's two probes over to the two terminals on R2. Record the voltage as V2.
8.Move the meter's two probes over to the two terminals on R3. Record the voltage as V3.
9.Did the electricity coming out of the battery have choice in the diagram below when the
meter was hooked up?
10.Hooking up the meter as a VOLTMETER can be described using which word (series or
parallel)?
11.Is there a common sense statement that your group can state that explains why R2's and
R3's voltages were equal?
Screen 65: Series/Parallel (V2)
COMBINATION SERIES/PARALLEL CIRCUITS:
1.Set the voltmeter's upper dial on the 30 scale
2.Set the voltmeter's lower dial on the DC Volts scale (red) and turn on the meter.
3.Connect the meter's black probe to the negative terminal on the battery, and then, connect
the meter's red probe to the positive terminal on the battery (does this picture below agree?).
4.If the probes were switched, was anything different on the voltmeter's reading?
5.Record the voltage on the battery.
6.Move the meter's two probes over to the two terminals on R1. Record the voltage as V1.
7.Move the meter's two probes over to the two terminals on R2. Record the voltage as V2.
8.Move the meter's two probes over to the two terminals on R3. Record the voltage as V3.
9.Did the electricity coming out of the battery have choice in the diagram below when the
meter was hooked up?
10.Hooking up the meter as a VOLTMETER can be described using which word (series or
parallel)?
11.Is there a common sense statement that your group can state that explains why R2's and
R3's voltages were equal?
Screen 66: Series/Parallel (V3)
COMBINATION SERIES/PARALLEL CIRCUITS:
1.Set the voltmeter's upper dial on the 30 scale
2.Set the voltmeter's lower dial on the DC Volts scale (red) and turn on the meter.
3.Connect the meter's black probe to the negative terminal on the battery, and then, connect
the meter's red probe to the positive terminal on the battery (does this picture below agree?).
4.If the probes were switched, was anything different on the voltmeter's reading?
5.Record the voltage on the battery.
6.Move the meter's two probes over to the two terminals on R1. Record the voltage as V1.
7.Move the meter's two probes over to the two terminals on R2. Record the voltage as V2.
8.Move the meter's two probes over to the two terminals on R3. Record the voltage as V3.
9.Did the electricity coming out of the battery have choice in the diagram below when the
meter was hooked up?
10.Hooking up the meter as a VOLTMETER can be described using which word (series or
parallel)?
11.Is there a common sense statement that your group can state that explains why R2's and
R3's voltages were equal?
Screen 67: Series/Parallel Ammeter
MEASURING CURRENT IN A SERIES/PARALLEL CIRCUIT
Note: the statistics that are typed into the light blue box below are for ONE circuit!
1.Objective: to use the meter as an ammeter and hook it up properly.
2.WARNING: Failure to read these directions carefully can result in a burned out fuse (it
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happens FAST). This experiment uses ONE RED TEST LEAD.
3.To measures amperes, set the meter's top dial at 300 mA and the bottom dial at DCmA
(GOLD scale).
4.Connect the meter's BLACK probe to the negative (-) terminal of the battery.
5.Use that ONE red test lead ONLY to connect the positive (+) terminal of the battery to R1.
6. Turn on the meter.
NOW NOTE where terminal "b" is below and ON your EQUIPMENT. Terminal "b" IS NOT either
end of the red test lead !!!
7.Using the red probe of the meter, TOUCH ONLY terminal "b" FIRST, RECORDING the
milliamperes registered on the meter in the "IT" boxes below.
9.DRAW a diagram of this circuit in your notes.
10.Notice that R2 and R3 are wired in parallel. Also: Notice that "IT" can be calculated by
using either V1 divided by R1 or V23 divided by R23.
Screen 68: Series/Parallel Analysis
SERIES/PARALLEL CIRCUIT ANALYSIS:
1.Notice that the 3 diagrams are drawn in steps such that the two parallel resistors R2 & R3
are treated as one resistor "R23" in the middle Circuit II and finally R1 and R23 are treated as
two series resistors added to calculate "RT" in Circuit III. The third circuit is used to calculate
"IT" or the total current. Since the total current must go through R1, V1=ITxR1. Remembering
that volts add in a series circuit (the middle circuit), then, V2=VT-V1. Now, since V2 = V3,
then I2 = V2/R2 and I3 = V3/R3. Then to check I2 and I3, IT = I2 + I3.
Screen 69: Battery Ri (volts)
APPLYING SERIES/PARALLEL CIRCUITS (to measure THE BATTERY'S INTERNAL
RESISTANCE):
1.As the battery, "VT", ages, it developes higher and higher internal resistance, shown as
"Ri" in the picture below.
2.The resistance, "Rb", of the bulb, B1 below, and the battery's internal resistance, "Ri" make
up a series circuit such that RT = Ri + Rb.
3.Also, the voltages add up such that VT=Vi + Vb with "Vi" being the voltage dropped across
"Ri" inside the battery.
THE EXPERIMENT:
4.Set the meter on DC Volts "30" scale and place the number 40 light bulb in the socket BUT
do not screw the bulb in all the way.
5.Use TWO red test leads to wire the bulb to the lantern battery.
5.Turn on the voltmeter and measure the volts across B1 before the bulb is screwed in all the
way. Record the OPEN CIRCUIT voltage, "VT", below.
6.While the voltmeter is still showing the volts across the UNLIGHTED bulb, screw in the bulb
and record the CLOSED CIRCUIT voltage, "Vb", below.
Screen 70: Battery Ri (amperes)
APPLYING SERIES/PARALLEL CIRCUITS (to measure THE BATTERY'S INTERNAL
RESISTANCE):
1.USE ONLY ONE red test lead to wire the positive (+) terminal of the battery to the light bulb.
2.Set the DC AMMETER on the "300" scale and the bottom dial on the GOLD DCmA setting.
3.Connect the meter's black probe to the negative (-) terminal of the battery.
4.Connect the meter's red probe to the remaining UNWIRED terminal of the light bulb. The bulb
should light (if the fuse has not be burned out). Record the amperes below.
5.Calculate the internal resistance of the battery.
Screen 71: Homemade VOM (Front + Back Views)
APPLYING SERIES/PARALLEL CIRCUITS (to design a homemade voltmeter and ammeter and
to learn their properties)
1.Examine the homemade meter. It is an electro-mechanical meter, also termed an analog
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meter since it gives a continous reading on its scale corresponding to the quantity being
measured. Previously, students used a digital meter - it has microchip circuitry that discretely
divides up a voltage range corresponding to a certain number of binary "bits".
2.The meter above, while primitive, will be used in p.73's circuit to get rather good readings,
so DON'T underestimate or skip this section.
3.The meter's left terminal is the common negative (-) terminal such that the student has to be
CAREFUL to use the TWO OUTSIDE terminals to measure volts and the LEFT & MIDDLE
terminals to measure amperes with the SHUNT resistor installed across those two terminals
(meter's DC rating is 5 mA).
4.Draw a view of the back-side circuitry of the meter BUT REVERSED so that the student has
TWO separate drawings - one drawing for the meter as a voltmeter and one drawing for the
meter as an ammeter.
5.Look closely at the front of the meter to see if you can see the tiny coil of copper wire that
rests on the needle between a little horseshoe magnet.
6.That copper coil has a resistance of 2150 ￿ and can ONLY handle 50 µA of CURRENT. The
50 µA is called FULL-SCALE DEFLECTION CURRENT. The meter acts like a 2150 ￿ resistor
carrying 50 µA. Using OHM's law, that equals .1075 volts!
Screen 72: Homemade VOM (volts circuit)
APPLYING SERIES/PARALLEL CIRCUITS (to design a homemade VOLTMETER and to learn its
properties)
1.The meter's left terminal is the common negative (-) terminal such that you have to be
CAREFUL to use the TWO OUTSIDE terminals to measure volts (the meter's rating: Vt = 5
volts).
2.The 50 µA is called FULL-SCALE DEFLECTION CURRENT. The 50µA reading then
corresponds to 5.0 volts. The meter is a 2150 ￿ resistor carrying 50 µA, which, using OHM's
law, equals .1075 volts. The meter's resistance, "Rm", is wired in series with "Rs." Since the
series "Rs" must "drop" Vs, Vs = VT - Vm or Vs = 5v - .1075v or Vs = 4.8925v, Therefore,
series resistor Rs = Vs/IT or Rs = Vs/50µA or Rs = 97850 ￿. Also, Rs = RT - Rm or Rs
=100,000 ￿ - 2150 ￿ or Rs = 97,850 ￿.
3.The meter is calibrated using a 1.5 volt dry cell which should give a reading of 15 (1.5v) on
the homemade voltmeter when the black plastic knob is turned to the correct point.
4.The meter has a "sensitivity" of 100,000 ￿ per 5 volts or 20,000 ￿/volt. While such
"sensitivity" is poor by today's digital VOM standards, as long as such a voltmeter's RT is 10x
greater than any resistor whose voltage "drop" is desired, the voltage measured is suitable
for 2-3 significant figures.
Screen 73: Homemade VOM (amperes circuit)
APPLYING SERIES/PARALLEL CIRCUITS (to design a homemade AMMETER and to learn its
properties)
1.The meter's left terminal is the common negative (-) terminal -- be CAREFUL to use the LEFT
and MIDDLE terminals to measure amperes (the meter's rating is IT = 5 mA).
2.The 50 µA is called FULL-SCALE DEFLECTION CURRENT. The 50µA reading then
corresponds to 5.0 mA on the homemade ammeter. Using Ohm's Law, the meter's movement
has a 2150 ￿ resistor multiplied by 50 µA (Im), or .1075 volts. The meter's resistance, "Rm", is
wired in parallel with the SHUNT resistor, "Rp." Since the parallel "Rp" must "share" IT, Ip = IT -
Im or Ip = .00495A. Therefore, Rp = Vm/Ip or Rp = 21.7￿.
3.The shunt, Rp, consists of a coil of nichrome wire attached to two-10￿ resistors wired in
series. The proper value for Rp is obtained by adjusting the length of nichrome wire between
the left and middle terminals.
4.The final resistance of this homemade milliammeter meter is... R = 1/(1/2150 + 1/21.7) or
21.5￿.
5.The meter is calibrated using a circuit consisting of a 6V lantern battery and a 1200￿
resistor or using a known value of mA measured with a digital meter.
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Screen 74: Homemade VOM (series V1)
MEASURING VOLTS WITH THE HOMEMADE VOLTMETER:
1.Using two red testleads and the two hookup wires, wire the three resistors in series with
the 6 volt battery.
2.Unlike the digital meter, this meter has POLARITY. So, wire the left terminal of the meter to
the (-) side of R1 and the right terminal of the meter to the (+) side of R1 and so on for R2 and
R3.
3.Check V1, V2, and V3 with the digital meter, TOO! Compare your results. Calculate the
percent difference between the homemade (analog) meter and the digital meter.
Screen 75: Homemade VOM (series It)
MEASURING AMPERES WITH THE HOMEMADE AMMETER:
1.Using one red testlead and the two hookup wires, wire the three resistors in series with
the 6 volt battery and the homemade ammeter as shown below.
2.The three R's were chosen to give an IT = 5mA with a fairly new 6.3 volt lantern battery.
This is because the circuit's RT ≈ 1272 ￿ (the resisitor's 1250￿ plus the 21.5￿ of the
homemade ammeter).
3.The same circuit should be checked with the digital meter. 4.Calculate the percent
difference between the two meters.
Screen 76: Homemade VOM (3-1 M ￿ R’s)
MEASURING VOLTS WITH THE HOMEMADE VOLTMETER:
1.Using two red testleads and the two hookup wires, wire the three resistors in series with
the 6 volt battery.
2.Unlike the digital meter, this meter has POLARITY. So, wire the left terminal of the meter to
the (-) side of R1 and the right terminal of the meter to the (+) side of R1 and so on for R2 and
R3.
3.Check V1, V2, and V3 with the digital meter, TOO! Compare your results. Calculate the
percent difference between the homemade (analog) meter and the digital meter.
4.COOPERATIVE LEARNING: It appears that the voltmeter is not correct. How can the same
equip- ment be used to get that home- made meter to read correctly with- out rewiring it
internally AND without changing those resistors or how the resistors are wired?
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