Edexcel IGCSE Physics: Electricity — Practice Questions

These are original questions written for Marlbridge, in the style and at the standard of the examination. They are not reproduced past-paper questions — examination boards hold copyright in their own papers. Use these alongside the official past papers available free from your board.

Related: Electricity revision notes

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Section A

1. State the equation linking power, current and voltage. [1]

2. State one similarity and one difference between how current and voltage behave in a series circuit compared with a parallel circuit. [2]

3. State how the resistance of a light-dependent resistor (LDR) changes as light intensity increases. [1]

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Section B

4. A 12 V supply is connected across a resistor, and a current of 0.40 A flows.

(a) Calculate the resistance of the resistor. [2] (b) Calculate the charge that passes through the resistor in 30 s. [2] (c) Calculate the energy transferred by the supply in that 30 s. [2]

5. A domestic appliance is rated at 230 V, 2.3 kW.

(a) Calculate the normal operating current of the appliance. [2] (b) State, with a reason, whether a 10 A fuse would be suitable for this appliance. [2] (c) Explain why the appliance requires a fuse rated close to, but above, its normal operating current, rather than a much higher-rated fuse. [2]

6. Two identical resistors are connected first in series, then in parallel, across the same 6.0 V battery.

(a) State whether the current drawn from the battery is larger in the series arrangement or the parallel arrangement. [1] (b) Explain your answer to (a). [3]

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Section C

7. A student rubs a plastic rod with a cloth. The rod becomes negatively charged.

(a) Explain, in terms of electrons, how the rod becomes negatively charged. [3] (b) State the charge acquired by the cloth, with a reason. [2] (c) The charged rod is brought close to a second, positively charged rod suspended freely. Describe and explain what happens. [3]

8. A technician investigates how current varies with voltage for three unlabelled components: a resistor, a filament lamp and a diode.

Describe how the current–voltage graph for each of the three components would differ, and explain the physical reason for each difference. [6]

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Worked answers

1. P = I V (power = current x voltage). [1]

2. Similarity/difference (either correct valid pair accepted): current is the same throughout a series circuit, but divides between branches in parallel; voltage is shared between components in series, but is the same across every branch in parallel. [2]

3. It decreases. [1]

4. (a) R = V/I = 12/0.40 = 30 Ω. [2] (b) Q = I t = 0.40 x 30 = 12 C. [2] (c) E = Q V = 12 x 12 = 144 J (or equivalently E = IVt = 0.40 x 12 x 30 = 144 J). [2]

5. (a) I = P/V = 2300/230 = 10 A. [2] (b) Not suitable: a 10 A fuse would blow under the appliance’s normal 10 A operating current (it needs to be rated above normal operating current, not equal to it), so a fuse rated slightly higher, such as 13 A, would be appropriate instead. [2] (c) A fuse rated close to normal operating current will blow quickly if a fault causes the current to rise even slightly above normal, protecting the wiring and the user; a much higher-rated fuse would allow a dangerously large fault current to keep flowing (and wiring to overheat) before the fuse finally blew. [2]

6. (a) Larger in the parallel arrangement. [1] (b) In parallel, both resistors are connected directly across the full 6.0 V, so each branch carries its own current at that voltage, and the total current drawn from the battery is the sum of both branch currents; in series, the same current has to pass through both resistors one after another, and the 6.0 V is shared between them, so each resistor only receives part of the voltage, giving a smaller current overall. The parallel arrangement therefore has a lower total (combined) resistance and so draws more current from the same battery. [3]

7. (a) Friction between the rod and the cloth transfers electrons from the cloth to the rod; since the rod gains electrons, it ends up with a net negative charge. [3] (b) The cloth becomes positively charged, because it has lost the electrons that were transferred to the rod, leaving it with a deficit of negative charge relative to positive charge. [2] (c) The two rods attract each other (or move towards each other), because the negatively charged rod and the positively charged rod carry unlike charges, and unlike charges attract. [3]

8. The resistor (at constant temperature) gives a straight line through the origin, because its resistance stays constant as current increases, so current is directly proportional to voltage. The filament lamp’s graph curves, flattening as voltage/current increases, because the filament heats up as more current flows, and its resistance rises with temperature, so progressively larger increases in voltage are needed to produce the same increase in current. The diode’s graph shows almost no current at all for voltage applied in one direction (reverse bias), then a sharp rise in current once a small forward voltage is exceeded (forward bias), because a diode is designed to conduct current in one direction only. [6] (2 marks per component: correct graph shape/behaviour plus the correct physical reason.)

Official syllabus

Pearson Education Ltd, Pearson Edexcel International GCSE in Physics (4PH1) Specification, Issue 4 — the same specification cited by the Electricity study guide and its revision notes. Always check the current specification for your examination year.