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Ohm’s Law
Engineering Science
Page 1
Introduction
Ohm’s Law is named after Georg Simon Ohm who was a
German Physicist and Mathematician. He discovered an
easy way to work out the Voltage, Current and
Resistance of a circuit. It is his theory that we still use
today.
Page 2
The Formula
The Formula that is used is V = I x R
Using the formula allows you to work out the Voltage of
a circuit if you know its Current and Resistance.
From this formula we can also swap around the values
to find Current (I) and Resistance (R)
Page 3
The Triangle
To remember all of the calculations, we can use a
formula triangle
This gives us a way to remember:
V=IxR
I=V/R
R=V/I
By covering up parts of the
triangle, we are left with the
calculation
Page 4
Values
Things that you need to remember are:
Voltage is measured in Volts with the unit V (eg. 25V)
Current is measured in Amps with the unit A (eg. 25A)
Resistance is measured in Ohms with the unit Ω (eg. 25 Ω)
Page 5
Example 1
What is the Voltage of the circuit?
270R
0.25A
Page 6
Example 2
What is the Current of the circuit?
270R
5000V
Page 7
Example 3
What is the Resistance of the circuit?
1.3A
200V
Page 8