Pearson Edexcel International GCSE in Physics · 4PH1 · Free · no account needed
Transformers — exam questions
10 original Incandio exam-style questions on transformers, 27 marks, about 27 minutes of writing. Each one carries the command word, the tariff and the specification statement it assesses, exactly as a paper presents them. This is an original Incandio practice question, written to reflect the structure and demands of the qualification. It is not an official Pearson Edexcel past-paper question.
This is the practice set for Transformers — the lesson that teaches it. Read the lesson first if the idea is new; come here when you want to find out whether you can turn it into marks. Completely free, no account needed to read.
What these questions ask of you
7 command words run through this set, and on Pearson Edexcel International GCSE Physics each one means something precise. Answering the wrong command is the commonest way a candidate who understands the lesson still loses the mark.
- Which (1 mark)
- one option chosen from the set given
- Name (1 mark)
- the correct quantity, unit or component
- Calculate (1–5 marks)
- select the equation, substitute, evaluate — and state the unit Misread as: giving a bare number with no equation and no unit
- Determine (1–4 marks)
- a value obtained by combining a reading or gradient with a relationship
- Explain (2–4 marks)
- the physics that causes it, set out as a line of reasoning Misread as: describing the change without giving the physical reason for it
- Suggest (1–3 marks)
- a plausible answer applying taught physics to an unfamiliar arrangement
- Describe (2–4 marks)
- developed, linked statements of what happens — including a named direction where one exists
Assessed on Paper 1 (4PH1/1P) and Paper 2 (4PH1/2P), against AO1, AO2, AO3.
Where these sit in the specification
Pearson Edexcel International GCSE Physics (4PH1) — statements 6.17 · 6.19 · 6.20 · 6.18. Incandio is aligned to this specification; it is not published by, endorsed by or affiliated with Pearson, and it reproduces none of Pearson's wording.
The 10 questions
Answer them on paper, then open the lesson's exam practice to have them marked. The mark scheme, the accepted and rejected answers and the annotated model answer are in Incandio and are not printed here — an answer beside its question is not practice.
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A power station generates 25 kV. A step-up transformer raises this for transmission along the grid, and step-down transformers at the far end reduce it again for local supply. The transformer at the power station has 2000 turns on its primary coil and 32 000 turns on its secondary.
Table 1 — the same power carried at three different transmission voltages Transmission voltage / kV Current in the cables / A Power wasted in the cables / kW 25 4000 16 000 132 758 574 400 250 63 (a)
(3)Calculate
Calculate the voltage the power station's transformer supplies to the transmission cables.
A power station generates 25 kV. A step-up transformer raises this for transmission along the grid, and step-down transformers at the far end reduce it again for local supply. The transformer at the power station has 2000 turns on its primary coil and 32 000 turns on its secondary.
Table 1 — the same power carried at three different transmission voltages Transmission voltage / kV Current in the cables / A Power wasted in the cables / kW 25 4000 16 000 132 758 574 400 250 63 ............................ kV
(b)
(2)Describe
Describe the relationship between transmission voltage and wasted power shown by Table 1.
A power station generates 25 kV. A step-up transformer raises this for transmission along the grid, and step-down transformers at the far end reduce it again for local supply. The transformer at the power station has 2000 turns on its primary coil and 32 000 turns on its secondary.
Table 1 — the same power carried at three different transmission voltages Transmission voltage / kV Current in the cables / A Power wasted in the cables / kW 25 4000 16 000 132 758 574 400 250 63 (c)
(3)Explain
Explain why the grid does not simply transmit at an even higher voltage than 400 kV.
A power station generates 25 kV. A step-up transformer raises this for transmission along the grid, and step-down transformers at the far end reduce it again for local supply. The transformer at the power station has 2000 turns on its primary coil and 32 000 turns on its secondary.
Table 1 — the same power carried at three different transmission voltages Transmission voltage / kV Current in the cables / A Power wasted in the cables / kW 25 4000 16 000 132 758 574 400 250 63 (Total for Question 1 = 8 marks)
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(1)Which
Which describes a step-up transformer?
Description A more turns on the primary than the secondary B more turns on the secondary than the primary C the same number of turns on both coils D a thicker wire on the secondary (Total for Question 2 = 1 mark)
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(1)Name
Name the material used for the core of a transformer.
(Total for Question 3 = 1 mark)
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(3)Calculate
A transformer has 500 turns on its primary and 1500 on its secondary. The primary voltage is 12 V. Calculate the secondary voltage.
secondary voltage = ............................ V
(Total for Question 4 = 3 marks)
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(3)Determine
A 100% efficient transformer takes 230 V at 0.60 A and supplies a device at 12 V. Determine the current supplied to the device.
current supplied to the device = ............................ A
(Total for Question 5 = 3 marks)
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(4)Explain
Explain why a transformer works with alternating current but not with direct current.
Figure 1 — a transformer (Total for Question 6 = 4 marks)
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(4)Explain
Explain why electricity is transmitted across the country at very high voltage.
(Total for Question 7 = 4 marks)
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(3)Suggest
Suggest why the charger is warm and what this means for its efficiency.
A laptop charger — A laptop charger plugged into the mains draws 0.35 A at 230 V and supplies the laptop with 19 V at 3.6 A. The plastic case is noticeably warm to the touch after a few minutes, even though nothing inside it moves.
(Total for Question 8 = 3 marks)
Have them marked, then defend the answer
Practice tells you the mark; teaching it back tells you whether you understand it. On Incandio a topic counts as mastered only once you have taught it and defended it.
- Mark these questions — 10 questions, marked on Incandio against the authored scheme, with the mistake you actually made named.
- Teach it — explain transformers to Ember, an AI pupil who does not have it yet and asks the awkward question.
- Defend it — argue it against Michael Faraday over three rounds, marked against descriptors you can read first.
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Back to the lesson
- Transformers — Two coils that never touch, the reason the National Grid runs at 400 000 volts, and why none of it works on a battery.
- All of Incandio Physics · Incandio Exam Practice