Question 11
(a) (i) State two differences between gravitational field and electric field.
(ii) List three methods by which electric charges could be produced.
(b) Two capacitors of capacitances 3 μF and 4 μF are connected in parallel and the combination connected in series with 2 μF capacitor. The p.d across the 3 μF capacitor is 12 V, when the arrangement is connected to a source of emf, E.
(i) Draw the circuit diagram of the arrangement.
(ii) Calculate the:
(I) Charge on the 2 μF capacitor;
(II) p.d across the 2 μF capacitor;
(III) value of E;
(IV) energy stored in the circuit.
(c) Describe how a lead-acid accumulator could be charged.
Observation
Part (a) Candidates performance was below average.
Part (b) Performance was below average.
Part (c) Candidates performance was below average.
The expected answers are:
(a) (i) Differences between gravitational field and electric field
- Gravitational field is a region around a mass while electric field is a region around a charge/charged body
- Gravitational field is always attractive while electric field is either attractive or repulsive
- Induction
- Friction/Rubbing
- Contact/Touch/conduction
(ii) Methods by which electric charges could be produced
(c) Charging lead-acid accumulator
A direct current is passed through the accumulator in a direction opposite to the direction in which the accumulator delivers current. This is done by connecting the positive terminal of the accumulator to the positive terminal of the direct current source and the negative terminal of the accumulator to the negative terminal of the direct current source.