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.
Learn this properly: Current, Voltage and ResistanceA student sets up a circuit to measure how the current through a filament lamp changes as the potential difference across it is increased in both directions. They then repeat the experiment with a diode and with a fixed resistor kept at constant temperature.
Describe and explain the shape of the current–potential difference (I–V) graph for each of these three components. Your answer should explain, in terms of the behaviour of the components, 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 at constant temperature depends on the potential difference across it. The results are shown below.
| Potential difference / V | Current / A |
|---|---|
| 0 | 0 |
| 1.5 | 0.30 |
| 3.0 | 0.60 |
| 4.5 | 0.90 |
| 6.0 | 1.20 |
(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 tells you about the resistor. (1 mark)
An electric kettle is connected to the 230 V mains supply. When it is switched on, a current of 9.0 A flows through it.
(a) Calculate the power of the kettle. Use P=IV. Show your working and give the unit. (2 marks)
(b) Calculate the energy transferred by the kettle in 120 s. Use E=Pt. (1 mark)
Two resistors, R₁ = 6 Ω and R₂ = 3 Ω, are connected in parallel with each other. This parallel combination is connected to a 12 V supply.
(a) Calculate the total resistance of the two resistors in parallel. Use RT1=R11+R21. (2 marks)
(b) Calculate the total current drawn from the supply. Use V=IR. (1 mark)
A thermistor is used as the temperature sensor in a circuit that switches on a cooling fan when a room gets too hot.
Explain how the resistance of the thermistor changes as the room temperature rises, and state what this does to the current in the sensor circuit. (2 marks)
Electric current is one of the fundamental quantities in a circuit.
State what is meant by the electric current in a circuit. (1 mark)