The number of turns in a coil is doubled, and the rate of change of flux through each turn is halved. How does the induced emf change?
Correct answer A. It stays the same
Topic / 30 questions
Electromagnetic Induction MCQs
Electromagnetic Induction MCQs cover Faraday's law, Lenz's law and energy conservation, motional emf, inductance, and the construction and use of transformers in power transmission. They help MDCAT, ECAT and FSc candidates revise concepts and short calculations, and every question on MCQs360 shows its correct answer instantly.
- Electromagnetic Induction 30
- Fluid Dynamics 30
- Electrostatics 30
- Electronics 30
- Electromagnetism 30
- Current Electricity 30
- Work and Energy 30
- Waves 30
- Vectors and Equilibrium 30
- Nuclear Physics 30
- Dawn of Modern Physics 30
- Thermodynamics 30
- Rotational and Circular Motion 30
- Atomic Spectra 30
- Alternating Current 30
- Force and Motion 30
A transformer with 1200 primary turns steps 230 V down to 11.5 V. How many turns are on its secondary?
Correct answer A. 60
The flux through each turn of a 100-turn coil changes by 4.0 mWb, producing an average emf of 2.0 V. How long did the change take?
Correct answer C. 0.20 s
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Which application makes use of eddy currents to produce a braking force?
Correct answer B. Electromagnetic braking in trains
Which of the following is equivalent to the henry, the unit of inductance?
Correct answer B. V s A⁻¹
Two coils have a mutual inductance of 0.20 H. The current in the first coil changes at 50 A/s. What emf is induced in the second coil?
Correct answer B. 10 V
How is flux leakage minimised in a practical transformer?
Correct answer B. By winding the coils close together on a closed soft-iron core
An ideal transformer steps 240 V down to 12 V. When the secondary current is 2.0 A, what is the primary current?
Correct answer D. 0.10 A
In a transformer, what are copper losses and how are they reduced?
Correct answer C. Heating in the windings due to their resistance, reduced by using thick copper wire
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In the national grid, what type of transformer is used near homes and factories?
Correct answer A. Step-down transformer
If the transmission voltage for a fixed power is increased by a factor of 10, by what factor is the power lost in the transmission lines reduced?
Correct answer D. 100
A power station sends 100 kW through cables of total resistance 5.0 Ω. What power is lost as heat in the cables if transmission is at 10 kV?
Correct answer D. 500 W
Why is electrical power transmitted over long distances at very high voltage?
Correct answer C. The current is reduced, so I²R losses in the cables are reduced
Which statement about a step-up transformer is correct?
Correct answer C. The secondary has more turns and carries a smaller current than the primary
A transformer takes 2.0 A from a 230 V supply and delivers 9.0 A at 46 V. What is its efficiency?
Correct answer A. 90%
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An ideal transformer has 500 turns on its primary and 2500 turns on its secondary. If the primary is connected to 230 V AC, what is the secondary voltage?
Correct answer D. 1150 V
Why is soft iron preferred to steel for the core of a transformer?
Correct answer D. It is easily magnetised and demagnetised, so hysteresis loss is small
Why is the iron core of a transformer laminated?
Correct answer A. To reduce energy losses due to eddy currents
Why does a transformer not work with a steady direct current in its primary coil?
Correct answer B. Steady current produces a constant flux, so no emf is induced in the secondary
A straight metal rod moves through a uniform magnetic field with its velocity parallel to the field lines. What emf is induced in the rod?
Correct answer C. Zero
About Electromagnetic Induction MCQs
Faraday's law questions ask when an emf is induced, for example with a magnet moving or stationary inside a coil, or a rod moving through a field, and what the negative sign in ε = −NΔΦ/Δt means. Lenz's law questions link the direction of induced current to energy conservation, including eddy-current braking of a magnet falling through a copper tube. Transformer questions cover the turns ratio, step-up and step-down transformers in the national grid, laminated soft-iron cores and the causes of copper, eddy-current and hysteresis losses. Power transmission calculations show why high voltage reduces I²R losses in cables.
Key facts to remember
- Faraday's law: the induced emf equals the rate of change of flux linkage, ε = −NΔΦ/Δt.
- Lenz's law: the induced current opposes the change that produces it, a consequence of conservation of energy.
- A rod of length L moving at speed v perpendicular to a field B has motional emf ε = BLv; no emf is induced if it moves parallel to B.
- For an ideal transformer, Vₛ/Vₚ = Nₛ/Nₚ = Iₚ/Iₛ.
- Power lost in cables is P = I²R, so raising the transmission voltage by a factor of n reduces the loss by n².
- The henry: 1 H = 1 V s A⁻¹ = 1 Wb A⁻¹.
Exams that include Electromagnetic Induction MCQs
Pakistan
- MDCAT
- ECAT (UET)
- NUMS
- AKU
- FSc boards
India
- NEET
- JEE Main
Bangladesh
- HSC
- Medical Admission Test
How to prepare for Electromagnetic Induction MCQs
- Remember that an emf is induced only while flux is changing; a stationary magnet inside a coil gives no reading.
- For transmission problems, find current from I = P/V first, then calculate I²R.
- Link each transformer loss to its cure: lamination for eddy currents, soft iron for hysteresis, thick copper wire for copper losses.
- Practise Lenz's law with a magnet entering and leaving a coil to fix the direction of induced current.
Frequently asked questions
Which exams ask Electromagnetic Induction MCQs?
Electromagnetic Induction is part of the FSc physics syllabus, so its MCQs appear in MDCAT, ECAT (UET), NUMS and AKU entry tests and in FSc board papers. Students in India meet the same ideas in NEET and JEE Main, and Bangladeshi students in HSC and the medical admission test.
Why is a transformer core laminated?
A changing magnetic flux induces eddy currents in a solid iron core, which waste energy as heat. Making the core from thin insulated sheets, or laminations, breaks up these current paths and greatly reduces eddy-current losses. Soft iron is used because it also has low hysteresis loss.
Last reviewed October 2026