Free Transformers questions for IGCSE Physics (0625), part of Electricity & magnetism. Each question has the answer and the marking points an examiner would look for.
Generate a full Transformers worksheet →All Electricity & magnetism questionsA step-down transformer is 100 % efficient. The output current is larger than the input current.
Why?
Answer: A
A transformer has 200 turns on the primary coil and 50 turns on the secondary coil. The input voltage is 6 V. What is the output voltage?
Answer: A
Electricity is transmitted over long distances at very high voltages.
Explain why a high voltage reduces energy losses in the cables.
State the type of transformer used at a power station.
| Part | Answer and marking points | Marks |
|---|---|---|
| (a) | smaller current, less I²R heating for the same power, a higher voltage means a smaller current B1 power lost in cables = I²R B1 so less energy is wasted as heat B1 | 3 |
| (b) | step-up step-up transformer B1 | 1 |
A generator supplies 50 kW of electrical power to a village through cables with a total resistance of 2.0 Ω. Transformers are used to change the voltage at which the power is transmitted.
Calculate the current in the cables and the power lost in them if the power is transmitted at 2500 V.
The generator output is 2500 V. Calculate the turns ratio of the transformer needed to step it up to 11000 V, assuming it is 100% efficient.
Explain how a transformer produces an alternating output voltage in the secondary coil.
Explain why a transformer does not work with a steady direct current.
| Part | Answer and marking points | Marks |
|---|---|---|
| (a) | 20.0 A; 800 W I = P/V = 20.0 A C1 P = I²R C1 800 W A1 | 3 |
| (b) | 1 : 4.40 Np : Ns = 2500 : 11000 = 1 : 4.40 B1 | 1 |
| (c) | alternating current in primary; changing magnetic field in iron core; induces e.m.f. in secondary an alternating current in the primary coil produces a changing magnetic field B1 the soft-iron core carries the changing field to the secondary coil B1 a changing field linking the secondary induces an (alternating) e.m.f. B1 | 3 |
| (d) | no changing magnetic field, so no induced e.m.f. a d.c. gives a constant magnetic field, so no e.m.f. is induced B1 | 1 |
Describe the structure of a simple transformer.
Name the three main parts.
Explain how a transformer produces an output voltage.
| Part | Answer and marking points | Marks |
|---|---|---|
| (a) | primary coil, secondary coil, iron core Any 2 of: primary coil; secondary coil; soft-iron core (all three = 2) B2 | 2 |
| (b) | a.c. → changing field in core → induced e.m.f. alternating current in the primary produces a changing magnetic field B1 the core carries the field to the secondary B1 the changing field induces an e.m.f. in the secondary B1 | 3 |
Fig. 6.1 shows a transformer.
Explain why a transformer only works with alternating current.
Use the information in Fig. 6.1 to calculate the output voltage.
State why the core is made of soft iron.
A power station transmits 2.0 × 106 W at 132 kV through cables of total resistance 10 Ω. Calculate the power lost in the cables.
Explain why electrical energy is transmitted at very high voltage.
| Part | Answer and marking points | Marks |
|---|---|---|
| (a) | a.c. produces a changing magnetic field in the core; changing field induces e.m.f. in secondary a.c. in the primary produces a changing magnetic field in the iron core B1 the changing field induces an e.m.f. in the secondary coil (d.c. gives a constant field) B1 | 2 |
| (b) | 24.0 V Vs/Vp = Ns/Np C1 24.0 V A1 | 2 |
| (c) | easily magnetised and demagnetised iron is easily magnetised and demagnetised / concentrates the magnetic field B1 | 1 |
| (d) | 2300 W I = P/V = 15.2 A C1 P = I²R C1 2300 W A1 | 3 |
| (e) | smaller current for same power; less energy lost as heat in cables (I²R) for the same power a higher voltage means a smaller current B1 power loss is proportional to I² so less energy is wasted heating the cables B1 | 2 |
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Meet Riyaz →Original Cambridge-style practice questions written for mentorriyaz.in. These are not Cambridge past paper questions, and this site is not affiliated with or endorsed by Cambridge University Press & Assessment. Updated 2026-11-04. Paper generator · mentorriyaz.in