24 past paper MCQs on The Transformer, from the Electromagnetic Induction unit of MDCAT Physics. The year each question appeared is shown where known; tap “Show answer” for the correct option and a short solution.
1.In a transformer there is no ______ connection between the two coils, but they are ______ linked. (MDCAT 2022)
Correct answer: (b) electrical, magnetically
The two windings are insulated from each other and the flux in the core is what couples them.
2.In principle, a transformer consists of two coils of copper, electrically insulated from each other, wound on the same: (MDCAT 2023)
Correct answer: (a) iron core
A soft iron core carries almost all the flux of the primary through the secondary.
3.In an ideal transformer: (MDCAT 2024)
Correct answer: (a) the power input is equal to the power output
An ideal transformer is lossless, so $V_pI_p=V_sI_s$.
4.In an ideal transformer, if the primary voltage is doubled and the turns ratio remains the same, what happens to the secondary current? (UHS MDCAT 2025)
Correct answer: (a) Doubles
The turns ratio doubles the secondary voltage too, and across the same load that doubles the secondary current.
5.In a step-up transformer, if the secondary voltage is increased by a factor of 10, the current in secondary coil will be: (SIBA MDCAT 2025)
Correct answer: (d) One-tenth of the primary current in transformer
Power is conserved in an ideal transformer, so ten times the voltage means a tenth of the current.
6.The basic principle behind the operation of the transformer is (KMU MDCAT 2024)
Correct answer: (b) Electromagnetic induction
A changing flux in the primary induces an emf in the secondary, which is mutual induction.
7.A transformer uses 220V line and delivers 22A at 1800V. Current drawn from line (100% efficiency)? (NUMS MDCAT 2024)
Correct answer: (b) 180A
Power is the same on both sides, so $1800\times22/220$ gives $180\,\mathrm{A}$.
8.Q.167 In transformer, there is no ______ connection between the two coils but they are ______ linked ? (UHS MDCAT 2023)
Correct answer: (b) Electrical, magnetically
The coils share no wire; they are coupled only by the flux in the common core.
9.Transformer works on the principle of: (SZABMU MDCAT 2023)
Correct answer: (c) Mutual Induction
The changing flux of the primary induces an emf in the secondary, which is mutual induction.
10.The efficiency of transformer is: (SZABMU MDCAT 2023)
Correct answer: (d) 90 %
A well made transformer wastes little, so its efficiency is around ninety per cent or better.
11.In principle, the transformer consists of two coils of copper, electrically insulated from each other, wound on the same? (UHS MDCAT 2023)
Correct answer: (a) Iron core
A soft iron core carries the flux from one winding to the other with little loss.
12.Power loss in the actual transformer is due to: (PMC MDCAT 2022)
Correct answer: (c) Eddy currents
Currents induced in the core itself waste energy as heat, which is why the core is laminated.
13.In step down transformer, current in secondary coil is ___ than current in primary coil: (PMC MDCAT 2022)
Correct answer: (c) Greater
Power is conserved, so a lower secondary voltage means a larger secondary current.
14.Transformer can convert _________ (PMC MDCAT 2022)
Correct answer: (d) AC voltage
A transformer works on a changing flux, so only alternating voltage can be transformed.
15.Eddy currents flow in: (PMC MDCAT 2022)
Correct answer: (b) Closed loops
Eddy currents circulate in closed loops within the body of the metal.
16.Q.71 Transformer works on the principle of: (NUMS MDCAT 2022)
Correct answer: (c) Mutual Induction
A changing flux in the primary induces an emf in the secondary, which is mutual induction.
17.If the supply frequency of a transformer increases, the secondary output voltage of the transformer: (PMC Practice 2021)
Correct answer: (c) Remains unchanged
The output depends on the turns ratio, and a higher frequency raises the induced emf per turn equally in both coils.
18.Step up transformer have ________ turns in secondary coil. (PMC Practice 2021)
Correct answer: (a) More
A step-up transformer has more turns on the secondary than on the primary.
19.The mutual induction happens in? (PMC Practice 2021)
Correct answer: (d) Transformer
The changing flux of the primary induces an emf in the secondary of a transformer.
20.Voltage in secondary winding is _____________ to the current in the secondary coil. (PMC Practice 2021)
Correct answer: (b) Inversely proportional
Power is the same on both sides, so a higher secondary voltage means a smaller secondary current.
21.Transformer is a device which steps up or steps down the input: (PMC MDCAT 2020)
Correct answer: (b) Voltage
A transformer changes the voltage; the power stays much the same.
22.In transmission from grid station, power losses are minimized by: (PMC MDCAT 2020)
Correct answer: (d) Increasing voltage
The loss is $I^2R$, so the voltage is stepped up and the current down for transmission.
23.If we give a direct current to the transformer’s primary coil, then there will be: (UHS MDCAT 2019)
Correct answer: (a) No emf produced in the secondary
A steady current gives a steady flux, and only a changing flux induces an emf.
24.In a practical transformer mutual induction between primary and secondary coils takes place. In such transformer what can be deduced about the power. (UHS MDCAT 2018)
Correct answer: (d) Power output < Power input
Some power is always lost as heat in the windings and the core, so the output falls short of the input.