1. 1
   A student connects a 12 V battery in series with two fixed resistors, resistor P (resistance 4 Ω) and resistor Q (resistance 8 Ω), to investigate the current and potential difference in a series circuit.

   (a)

   What is the total resistance of the circuit?

   [1 mark]

   • A4 Ω
   • B8 Ω
   • C12 Ω
   • D32 Ω

   (b)

   What is the current in the circuit?

   [1 mark]

   • A0.5 A
   • B1 A
   • C1.5 A
   • D3 A

   (c)

   Calculate the potential difference across resistor P, and state how this potential difference compares with the potential difference across resistor Q and the battery.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A student connects two resistors, each of resistance 6 Ω, in parallel across a 12 V power supply, to investigate current in parallel circuits.

   (a)

   What is the current through each 6 Ω resistor?

   [1 mark]

   • A0.5 A
   • B1 A
   • C2 A
   • D4 A

   (b)

   Compared with connecting the same two resistors in series, connecting them in parallel instead...

   [1 mark]

   • Aincreases the total resistance of the circuit
   • Bhas no effect on the total current drawn from the supply
   • Ckeeps the total resistance of the circuit the same
   • Ddecreases the total resistance of the circuit

   (c)

   Calculate the total resistance of the two 6 Ω resistors connected in parallel.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A student investigates how the resistance of a thermistor and a light-dependent resistor (LDR) change under different conditions, using a circuit in which an ammeter and a voltmeter are connected to measure the current through, and potential difference across, the component under test, with the p.d. across the component held constant.

   (a)

   Describe how the resistance of the thermistor changes as its temperature increases, and explain why this happens in terms of the movement of charge carriers.

   [3 marks]

   (b)

   Describe how the resistance of the LDR changes as light intensity increases, and explain the effect this has on the current in the circuit if the potential difference across the LDR is kept constant.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   An engineer is comparing how a fixed resistor, a filament lamp and a diode each behave when connected in turn into a test circuit containing a battery, an ammeter and a voltmeter, as the potential difference across the component is gradually increased from 0 V and then reversed in direction.

   (a)

   Explain how the current varies with potential difference for a fixed resistor, a filament lamp and a diode, and explain the physical reason for the behaviour of each component.

   [6 marks]

   (b)

   Evaluate why a thermistor, rather than a fixed resistor, would be more suitable for use in a circuit designed to automatically switch on a heater when the temperature falls below a set value, referring to how the resistance of each component changes.

   [6 marks]

   Total for question 4: 12 marks

End of questions