DC Circuits - Teachers.ocps.net

Electronics - Devices

Oct 5, 2013 (4 years and 9 months ago)

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1

DC Circuits

Name ________________________________________ Date_______ Period ____

A
.
Ohm’s Law

1
. Construct a circuit consisting of a battery, an ammeter, and a resistor. Vary the
voltage and record the current measure
d

by the ammet
er in the table below.

Trial

Voltage (Volts)

Current (Amps)

Trial

Voltage (Volts)

Current (Amps)

1

7

2

8

3

9

4

10

5

1
1

6

12

2
. Draw a graph of voltage versus current.

(Note: Your axes label may be different
.
)

(a)

What type o
f relationship exists between the voltage and the current?

(b)

Determine the slope of your graph.

Slope of
graph _________________

(c)

What is the value of the resistor used in your circuit?

R = _________________

(d)

How does the slope of your graph compare with
the value of the resistor in your
circuit?

2

B
.
Resistors in Series

1.

Construct a circuit consisting of a battery
, an ammeter, and 3 resistors having
different resistance values

(R
1
, R
2
, and R
3
)
.

Connect all circuit elements in

series.
Draw a circuit diagr

2.

Set the terminal (battery voltage) at a
fixed

value for this part of the investigation.

a.

With the ammeter connected between the + terminal of the battery and the
first resistor in the circuit, measure the current. Record this as I
t

(the

total
current in the circuit).

b.

Remove the ammeter and connect it between the first

(R
1
)

and the second
(R
2
)
resistors in the circuit. This is the current through R
1
. Record this
value for I
1

in the table
.

c.

Next, connect the ammeter between resistors R
2

a
nd R
3

to measure the
current I
2

through resistor R
2
.

Record this current for I
2

in the table.

d.

Finally, connect the ammeter between R
3

and the negative terminal of the
battery to measure the current I
3

through resistor R
3
.

Record I
3
.

3.

Repeat step 2 above fo
r
two more

set
s

of three different resistors R
1
, R
2
, and R
3
.
Record your data in the table below.

Record the battery voltage as V
t
.

I
t

=

I
1

=

I
2

=

I
3

=

Trial

R
1

R
2

R
3

R
1

+ R
2

+ R
3

V
t
/ I
t

1

2

3

Trial

V
1

V
2

V
3

V
1

+ V
2

+ V
3

V
t

1

2

3

Questions
:

1.

What can conclude about the current through each resistor?

2.

What is the relationship between the sum of the voltage drops across the
resistors and the battery voltage?

3.

Is it possible to replace the three resistors by one resi
stor such that the
total current, I
t
,

remains the same? If possible, what should the value of
this resistor be?

3

C.

Resistors in Parallel

1.

Construct a circuit consisting of a battery, an ammeter, and 3 resistors having
different resistance values (R
1
, R
2
, and R
3
). Connect all circuit elements in
parallel. Draw a circuit diagram of your circuit.

2.

Set the terminal (battery voltage) at a
fixed

value for this part of the investigation.

a.

With the ammeter connected to the

+ terminal of the battery and the
junct
ion between the first and second resistors in the circuit, measure the
current. Record this as I
t

(the total current in the circuit).

b.

Remove the ammeter and connect it in the first branch containing only R
1

in the circuit. This is the current through R
1
.
Record this value for I
1

in the
table
.

c.

Next, connect the ammeter in the second branch containing resistor R
2

to
measure the current I
2

through resistor R
2
.

d.

Finally, connect
in the branch containing resistor

R
3

to measure the current
I
3

through resistor R
3
.

e.

Use the voltmeter to measure the voltage drop across each resistor.

3.

Repeat step 2 above for
two more

set
s

of three different resistors R
1
, R
2
, and R
3
.
Record your data in the table below. Record the battery voltage as V
t
.

V
1

=

V
2

=

V
3

=

V
t

=

Trial

R
1

R
2

R
3

V
t
/ I
t

1

2

3

Trial

I
1

I
2

I
3

I
1

+
I
2

+
I
3

I
t

1

2

3

Questions
:

4.

What can
you
voltage drop across

each resistor?

5.

What is the relationship between the
total current and

the currents through
the individual resistors
?

6.

Is it possible to replace the three resistors by one resistor such that the
total current, I
t
,

remains the same? If possible, what should the value of
this resistor be?

4

Ser
ies Circuit Diagram
:

Parallel Circuit Diagram
: