Answers to AQA GCSE Potential difference, Current and Resistance

Practice Questions

1.What is potential difference a measure of in a circuit?

Potential difference is a measure of the amount of energy per unit charge.

2.Describe how resistance occurs in a circuit

At room temperature the positive metal ions have kinetic energy, so they are vibrating about a fixed position.

The delocalised electrons are trying to move through the structure between the positive metal ions.

These vibrating  metal ions resist the movement of electrons through the structure causing resistance.

3.Name 3 circuit components that would have resistance

Any three circuit components e.g. bulb, resistor, fuse

4. A bulb as a current of 900mA and a resistance of 2 ohms. Calculate the potential difference across the bulb.

Convert 900mA to A. 

1A = 1000mA, so 900mA = 0.9A.

Potential difference = Current x Resistance

Potential difference = 0.9A x 2Ω

Potential difference = 1.8V