AQA GCSE Physics (8463), Higher tier · Magnetism and electromagnetism › Induced potential and transformers
Practise Transformers. 14 exam-style questions plus unlimited generated ones on this subtopic, at up to four difficulty levels, with full mark schemes and a progress tracker. Free, no account needed.
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Name the material usually used for a transformer's core.
Soft iron.
Sample questions
Written for this site in the style of AQA exam questions. They are not taken from real past papers.
Question 1Easy2 marks
(a) A transformer has more turns on its secondary coil than its primary coil. What type of transformer is it? Tick (✓) one box.[1]
Step-up
Step-down
Neither — this is impossible
It depends on the current
(b) Name the material usually used for a transformer's core.[1]
Show the answer and mark scheme
(a)Answer: Step-up
(b)Answer: Soft iron.
(soft) iron
Question 2Medium8 marks
A transformer is used to operate an 11.5 V lamp from the 230 V mains supply. The primary coil has 2000 turns.
(a) Is this a step-up or a step-down transformer? Give a reason for your answer.[2]
(b) Calculate the number of turns on the secondary coil. Use the Physics Equations Sheet.[3]
(c) The transformer is 100% efficient. The current in the lamp is 2.0 A. Calculate the current in the primary coil. Use the Physics Equations Sheet.[3]
Show the answer and mark scheme
(a)Answer: Step-down: the output pd is less than the input pd.
step-down
the output potential difference is smaller than the input potential difference
(b)Answer: 100 turns
230 ÷ 11.5 = 2000 ÷ ns
ns = 2000 × 11.5 ÷ 230
100
(c)Answer: 0.10 A
230 × Ip = 11.5 × 2.0
Ip = 23 ÷ 230
0.10 (A)
Question 3Hard9 marks
A laptop charger contains a transformer. The output of the transformer is 19 V and 3.4 A. The input is from the 230 V mains supply.
(a) Calculate the output power of the transformer.[2]
(b) Assume the transformer is 100% efficient. Calculate the current in the primary coil. Use the Physics Equations Sheet.[3]
(c) The primary coil has 1840 turns. Calculate the number of turns on the secondary coil. Use the Physics Equations Sheet.[2]
(d) In practice, the charger becomes warm when it is used. Explain what this means for the actual current in the primary coil.[2]
Show the answer and mark scheme
(a)Answer: 64.6 W
P = 19 × 3.4
64.6 (W)
(b)Answer: 0.28 A (0.281 A) A
230 × Ip = 19 × 3.4
Ip = 64.6 ÷ 230
0.28 (A)
(c)Answer: 152 turns
ns = 1840 × 19 ÷ 230
152
(d)Answer: Some energy is wasted as heat, so the input power, and therefore the primary current, is larger than calculated.
the transformer is not 100% efficient; some energy is dissipated (as thermal energy)
so the input power is greater than 64.6 W, and the primary current is greater than 0.28 A