Download Intro. to Electricity File

Electricity
Skill Trades 1201
Parts of An Atom

Electrons are negatively charged particles that
orbit around the nucleus.

Protons are positively charged.

Opposite charges attract.

Electricity occurs when electrons flow from one
atom to another.
Voltage
Voltage is a measure of the Electromotive
Force (EMF) in electricity.
 EMF is the electric force that "pushes"
electrons around a circuit.

Voltage

Measured in volts (v).

Algebraic Symbol: E or V

Graphic Symbol:
~
_
+
Current

Current is a measure of the rate of electron
flow through a material.

Measured in amps (a).
Current

Algebraic Symbol: I = intensity

Graphic Symbol:
A
Resistance


Resistance is the property of matter
which opposes the flow of electrons.
Measured in ohms ().
Resistance

Algebraic Symbol: R

Graphic Symbol:
Conductors
Conductors have a large number of
loosely attached electrons that can move
very easily from one atom to another.
 Examples:

 Gold
 Copper
 Aluminum
 Water
Insulators



Material with a high resistance to electrical
current.
Electron orbits are very close to the nucleus.
Examples:
 Plastic
 Rubber
 Glass
 Wood
Electrical Circuit

For electricity to flow, there must be a
complete path. Therefore it must have:

Conductor (e.g. Copper wire)
 Energy Source (e.g. Battery)
 Load (e.g. Light)
 Control Device (e.g. Switch)
Electrical Circuit
Ohm’s Law

Ohms Law is a mathematical equation
explaining the relationship between
Voltage, Current, and Resistance.
Ohm’s Law

The relationship is expressed as
E

=I*R
Where
E
is Electromotive Force measured in Volts
 I is Electrical Current measured in Amperes
 R is Electrical Resistance measured in Ohms
Ohm’s Law
E
I
R
Calculation

Using Ohm's Law equation, calculate
Resistance, where:
E

= 120 volts, I = 15 amps
Answer:
R
= E/I
 R = 120 v / 15a
R
=8
Power
Power is the ability of electricity to perform
work.
 Measured in watts (W)
 Algebraic Symbol: P

Power Law

The relationship is expressed as:
P

=IxE
Where…
P
is Power measured in Watts.
 I is Electrical Current measured in Amperes.
 E is Electromotive Force measured in Volts.
Power Law
P
I E
Calculation

Using Power equation, calculate Current (I),
where:
E

= 120 volts and P = 800 w
Answer:
I
= P/E
 I = 800 w / 120 v
 I = 6.67 amps
Types of Circuits

Series
A

Parallel
A

single path for current to flow.
single voltage shared by multiple loads.
Complex
 Combinations
of series and parallel circuits.
Series Circuit
R1
_
I
R2
E
+
R3
Simple Parallel Circuit
I
_
E
I1
R1
+
I2
R2
Electrical Tools

Wire Strippers/Crimpers

Insulated Screwdrivers
Electrical Tools

Wire sheathing stripper

Marrettes / Wire Nuts
Electrical Tools

Lineman Pliers

Needle Nose Pliers
Electrical Tools

Octagon / Junction Box

Switch Box
Electrical Tools
Electricity
Skill Trades 1201