A brief overview on the basics
jbugni@nmu.edu
The Atom
Basic unit of matter
Made up of tiny particles, two are important in
electricity
Protons
Contained in the nucleus (center) of the atom
Have a positive charge
Electrons
Move around the nucleus in paths called shells
Have a negative charge
Electrons in the outer most shell are called valence electrons
The Atom cont.
Amount of negative charge of each electron is equal to the
amount of positive charge of each proton
If enough energy is applied to an atom, some valence
electrons will leave the atom
Ions
Charge atom
Negative ion has more electrons than protons
Positive ion has more protons than electrons
Ions with similar charges repel, different charges attract
Current flows when electrons move from one atom to
another
The Atom cont.
http://nasash.com/physics_thesaurus/wp

content/uploads/2008/06/a4atom.jpg
What is a circuit?
Defined as a system of conductors and devices through
which electrons can move.
Consists of three characteristics
Must contain a power source
Complete path for current flow from one side of the
power source to the other
Contains some type of resistance to limit the amount of
current.
Example of basic circuit
Light bulb
Switch
Conductor
Battery
http://phet.colorado.edu/simulations/sims.php?sim=Circuit_Construction_Kit_
DC_Only
Voltage
Measured in volts
Electrical pressure used to move electrons throughout
the circuit
Also defined as the potential difference between two
unlike charges
Think of voltage as the water pressure in a garden hose
Current
Measured in amps or ampere
Movement of electrons through the circuit
Think of the water flow in the garden hose
DC refers to direct current or movement of electrons in
one direction
Resistance
Measured in ohms
Opposes the movement of current
Reduces the amount of current in a circuit
Think of kinking the garden hose
May also be referred to the load of the circuit
Conductors
A solid, liquid or gas which electrons can easily pass
through
Most commonly made from copper
Schematic Diagrams
Standard way of communicating information in
electricity and electronics
Components are shown by graphic symbols
May not accurately represent the actual location of
components
Electrical Symbols
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144
051240
Example of Schematic
http://alldatapro.com/alldata/PRO~V156153136~C21290~R0~OD~N/0/41746505/42420070/42420075/42420077/34853741/34869956/34869958/
564
73437
Ohm’s law
Discovered by German physicist Georg Simon Ohm
Shows the relationship of resistance (R), current (I) and
voltage (E) along with power (W)
The most common equation is E=IR, where voltage is equal
to resistance times current
Basis for all study of electrical properties
Ω
Ohm’s law
http://www.uakron.edu/groups/chemcar/docs/ohm.pdf
E=IR
For example: If a circuit has a constant power source
of 12 volts and 4 amps of current, the resistance of the
circuit must be 3 ohms (
Ω
)
12=4
×
R therefore R=12
÷
4=3
http://alldatapro.com/alldata/PRO~V155748232~C35580~R0~OD~N/0/80851247/83211660/83214935/83214937/34853741/34869214/34869215/
348
69322/34869325/146660096
Series Circuit
Only one path for current to flow
Total resistance of circuit is the sum of all resistances
Current is consistent throughout the circuit
Total voltage is spread across the loads in the circuit
Voltage drop is amount of voltage required to force the
current through the load or resistance
Sum of all the voltage drops equals the total voltage
applied to the circuit
Series Circuit Schematic
http://www.cybermike.net/reference/liec_book/DC/00090.jpg
Parallel Circuit
Contain multiple connections or branches
Loads operate independently
Total current is divided between the branches
Determined by the resistance of the branch
Calculated by Ohm’s law
Voltage is the same on all the branches
Total resistance decreases as more branches are added
Always less than the branch with lowest resistance
Parallel Circuit cont.
Resistance formulas
Two resistances of unequal value
RT=(R1
×
R2)
÷
(R1 + R2)
All resistances are equal in value
RT = (value of one resistance)
÷
(number of resistances)
If resistances are not all equal in value
RT = 1
÷
(1/R1 + 1/R2 + 1/R3 + … + 1/RN)
Parallel Circuit Schematic
http://www.faqs.org/docs/electric/DC/00083.png
Series

Parallel Circuit
Combination of both series and parallel circuits
Requires formulas from both series and parallel
circuits to calculate resistance, current and voltage
drops
Most electrical devices have series

parallel circuits
Series

Parallel Schematic
http://www.faqs.org/docs/electric/DC/00123.png
Other sources
Buban, P., Schmitt, M. L., & Carter Jr., C. G. (1992).
Understanding Electricity and Electronics Technology.
Peoria: Macmillan/McGraw

Hill.
Grob, B. (1992).
Grob Basic Electronics.
Westerville:
Macmillan/McGraw

Hill.
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