Electrical Resistance

Key Stage 3

Resistance is a description of how difficult it is to increase the current through a conductor when increasing the potential difference.

The unit of resistance is the Ohm (Ω).

Resistance cannot be directly measured. Resistance must be calculated by dividing the Potential Difference by the Current.

Conductors have a low resistance and insulators have a high resistance.

\[Resistance = \tfrac{Potential Difference}{Current}\] \[R = \tfrac{V}{I}\] Where:

R = Resistance

V = Potential Difference

I = Current

A student measures a potential difference of 5V across a component and a current of 0.1A. Calculate the resistance.	A bulb has a current of 200mA passing through it and a potential difference of 12V across it. Calculate the resistance of the bulb.	Calculate the resistance of a buzzer connected in series to a 6V battery with an ammeter reading of 10mA.
Potential Difference = 5V Current = 0.1A \[R = \tfrac{V}{I}\] \[R = \tfrac{5}{0.1}\] \( R = 50 \ohm\)	Force = 10,000N Distance moved in the direction of the force = 15m \[R = \tfrac{V}{I}\] \( W = 10,000 \times 15\) \( W = 15,000J\)	Force = 40N Distance moved in the direction of the force = 0m \[R = \tfrac{V}{I}\] \( W = 20 \times 0\) \( W = 0J\) No work has been done because the movement is not in the direction of the force. The weight acts downwards but the movement was horizontal.