1. 1
   A copper wire of length 2.5 m and uniform cross-sectional area 1.0 × 10⁻⁶ m² carries a steady current of 3.0 A for 2.0 minutes. The resistivity of copper is 1.7 × 10⁻⁸ Ω m.

   (a)

   How much charge flows through the wire in this time?

   [1 mark]

   • A6.0 C
   • B40 C
   • C360 C
   • D2.3 × 10²¹ C

   (b)

   What is the resistance of the wire?

   [1 mark]

   • A6.8 × 10⁻¹⁵ Ω
   • B4.3 × 10⁻² Ω
   • C1.7 × 10⁻² Ω
   • D24 Ω

   (c)

   Calculate the energy dissipated in the wire during the 2.0 minutes.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A student measures the current in a fixed resistor and in a small filament lamp at different potential differences. For the resistor: 1.0 V gives 0.050 A, 2.0 V gives 0.100 A and 4.0 V gives 0.200 A. For the lamp: 1.0 V gives 0.10 A, 2.0 V gives 0.15 A and 4.0 V gives 0.20 A.

   (a)

   Which statement about the two components is correct?

   [1 mark]

   • ABoth components are ohmic
   • BThe resistor is ohmic; the resistance of the lamp decreases as the potential difference increases
   • CThe lamp is ohmic; the resistor is non-ohmic
   • DThe resistor is ohmic; the resistance of the lamp increases as the potential difference increases

   (b)

   The resistor and lamp are connected in series to a supply of negligible internal resistance, and the current is 0.20 A. What is the emf of the supply?

   [1 mark]

   • A8.0 V
   • B4.0 V
   • C6.0 V
   • D2.0 V

   (c)

   The resistor and the lamp are instead connected in parallel across a 2.0 V supply of negligible internal resistance. Determine the total current from the supply and deduce which component dissipates more power.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A student investigates a chemical cell by connecting a variable resistor directly across its terminals and measuring the terminal potential difference with a voltmeter of very high resistance. With the variable resistor set to 10.0 Ω the potential difference is 1.43 V. With it set to 2.0 Ω the potential difference is 1.20 V.

   (a)

   Determine the emf and the internal resistance of the cell.

   [3 marks]

   (b)

   The student claims that the smaller the resistance of the variable resistor, the greater the power the cell delivers to it. Evaluate this claim.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A camper-van heater runs from a 12.0 V battery (emf) of internal resistance 0.050 Ω. The heater contains two identical heating elements, each of resistance 1.2 Ω, which a switch can connect as a single element, as both elements in series, or as both elements in parallel. The resistances of the elements can be taken as constant.

   (a)

   Determine the power delivered to the heating elements for each of the three switch settings, and hence identify the highest heat setting.

   [6 marks]

   (b)

   The heater is connected to the battery by copper cable; the total length of conductor in the circuit is 6.0 m and its cross-sectional area is 1.5 mm². The resistivity of copper is 1.7 × 10⁻⁸ Ω m. Discuss how the internal resistance of the battery and the cable affect the heater's performance on its highest setting, and suggest how the cable should be chosen.

   [6 marks]

   Total for question 4: 12 marks

End of questions