Download OHMS LAW

Ohm’s Law explains the
relationship between voltage (V ),
current (I) and resistance (R)
 Used by electricians, automotive
technicians, stereo installers


It is the push or pressure behind
the current flowing through a
circuit.
 Measured

in (V) volts.
How you should be thinking
about electric circuits:
Voltage: a force that
pushes the current
through the circuit
(water pump pushing
water through hose)

Current refers to the quantity
(amount) of electrical flow.
 Measured
in Amps (A)
How you should be thinking
about electric circuits:
Current: the actual
“substance” that is
flowing through the
wires of the circuit
(electrons!)
(like the water in the
river)

Resistance to the flow of the
current.

Measured in Ohms
How you should be thinking
about electric circuits:
Resistance: friction that
impedes the flow of
current through the
circuit (rocks in the
river)

1. Assuming the resistance does not
change:
As voltage increases, current increases.
 As voltage decreases, current decreases.


2. Assuming the voltage does not change:
As resistance increases, current decreases.
 As resistance decreases, current increases.


Let's see how this works

V = IxR

I=V/R

R=V/I



Battery voltage is 12V
Resistance 2 Ohm
What is the Current?
Given: V = 12 V
R = 2Ω
Unknown: I = ?
Formula: I = V / R
Solve: I = 12V / 2Ω
Solution: 6 A (6 amps)



Voltage is 12V
Current is 4 Amps
What is the Resistance?
Given: V = 12V I = 4 A
Unknown: R = ?
Equation: R = V / I
Solve: R = 12V / 4A
Solution: R = 3Ω
Multi meters/ DVOM

Why do we need resistors

Slow down current or decrease the voltage levels in
a circuit.
 Creates a voltage drop that pushes current
 Prevents damage
 Used to produce heat and/or light
What is Voltage?
 What is Current?
 What is Resistance?




Series circuit :
One pathway for current to flow.
Example: Old Christmas lights


More then one path way for current to
flow.
Used in most electrical vehicle circuits.

Let’s watch a video about electricity to review
all that we have learned.