Prescribed practical P6 - Section 3


We can see from the graph that as the current increases the voltage also increases.

This agrees with our prediction.

In fact, since the line of best fit is a straight line through the origin, we can be even more precise.

We can say that the voltage across the wire is directly proportional to the current flowing through it.

As the voltage increases the current increases in direct proportion.

This is known as Ohm’s Law.

Ohm’s Law state that the voltage across a conductor is directly proportional to the current flowing through it, provided all physical conditions, such as temperature, remain constant.

A conductor that obeys Ohm’s Law is called an ohmic conductor.

Copper or constantan wire are examples of ohmic conductors.


Illustration of triangle showing Ohm's law components - voltage v, current i and resistance r

Current, voltage and resistance are related by the equation:

voltage V = current I x resistance R


V = voltage in V

I = current in A

R = resistance in \Omega

V = IRV = I x R
I = \frac{\text{V}}{\text{R}}I = V ÷ R
R = \frac{\text{V}}{\text{I}}R = V ÷ I
Move on to Video