AQA GCSE Combined Science: Physics: Electricity
6 exam-style questions with full mark schemes and model answers. Write your own answer and the AI examiner marks it against the mark scheme.
A student connects three components in turn into a test circuit and records how the current through each one changes as the potential difference across it is increased in both directions. The three components are a fixed resistor at constant temperature (an ohmic conductor), a filament lamp, and a diode.
Describe the shape of the current–potential difference (I–V) graph for each of these three components, and explain why the filament lamp and the diode do not give a straight line through the origin. (6 marks)
A student investigated how the current through a fixed resistor depends on the potential difference across it, keeping the resistor at a constant temperature. The results are shown below.
| Potential difference / V | Current / A |
|---|---|
| 0 | 0 |
| 2.0 | 0.25 |
| 4.0 | 0.50 |
| 6.0 | 0.75 |
| 8.0 | 1.00 |
(a) Using a pair of values from the table, calculate the resistance of the resistor. Use V=IR. Show your working and give the unit. (3 marks)
(b) State what the shape of a current–potential difference graph of these results would tell you about the resistor. (1 mark)
An electric heater is connected to the 230 V mains supply. When it is switched on, a charge of 9000 C flows through it in 5 minutes.
(a) Calculate the current in the heater. Use Q=It (remember to convert the time to seconds). Show your working and give the unit. (2 marks)
(b) Calculate the power of the heater. Use P=IV. (1 mark)
Two resistors, R₁ = 4 Ω and R₂ = 2 Ω, are connected in series with a 6 V cell. An ammeter is connected in the circuit.
(a) Calculate the total resistance of the circuit. (1 mark)
(b) Calculate the current read by the ammeter. Use V=IR. (2 marks)
An outdoor security light contains a light-dependent resistor (LDR) as a sensor.
Explain how the resistance of the LDR changes between bright daylight and darkness, and state which condition the light is designed to switch on in. (2 marks)
The mains electricity supply to homes in the UK is an alternating current (a.c.) supply.
Define what is meant by an alternating current. (1 mark)