All Free Electrical Engineering MCQs with Answers

• A. Brass
• B. Copper
• C. Zinc
• D. Ebonite

Explanation: Ebonite is essentially non-magnetic, with permeability approximately equal to that of free space.

• A. non-magnetic substances
• B. diamagnetic substances
• C. ferromagnetic substances
• D. none of the above

Explanation: Magnetic susceptibility is positive for paramagnetic and ferromagnetic materials because they are attracted by an applied magnetic field.

• A. resistance of the coil
• B. motion of the magnet
• C. number of turns of the coil
• D. pole strength of the magnet

Explanation: By Faraday's law, induced emf depends on the rate of change of flux linkage, including motion, number of turns, and magnet strength.

• A. 240 N
• B. 24 N
• C. 2.4 N
• D. 0.24 N

Explanation: The force on a current-carrying conductor is F = BIL sinθ. With B = 0.8 T, I = 10 A, L = 0.3 m, and θ = 90°, F = 0.8 × 10 × 0.3 = 2.4 N.

• A. 2500 AT/m
• B. 250 AT/m
• C. 25 AT/m
• D. 2.5 AT/m

Explanation: Magnetic field strength is H = NI/l, so H = (50 × 1)/0.2 = 250 ampere-turns per metre.

• A. 100 N
• B. 10 N
• C. 1 N
• D. 0.1 N

Explanation: For two parallel conductors, force per metre is F/L = μ₀I₁I₂/(2πd). Substitution gives (4π × 10⁻⁷ × 100 × 100)/(2π × 0.02) = 0.1 N/m.

• A. copper
• B. aluminium
• C. soft iron
• D. brass

Explanation: Soft iron has high permeability, so it provides an easy path for magnetic flux and diverts the field away from the screened region.

• A. Kirchhoffs law
• B. Lenz's law
• C. Ampere's law
• D. Faraday's laws

Explanation: Ampère's law relates current to the magnetic field around it, while the Biot-Savart law gives the field contribution from each small…

• A. less than that of disc but in opposite direction
• B. equal to that of disc and in the same direction
• C. equal to that of disc and in the opposite direction
• D. less than that of disc and in the same direction

Explanation: The rotating copper disc produces eddy currents whose magnetic field opposes the relative motion of the needle.

• A. 2
• B. 4
• C. 6
• D. 8

Explanation: Ampere-turns equal NI, so the current is I = 3200/800 = 4 A. The correct value is therefore option b.

• A. ferromagnetic
• B. paramagnetic
• C. diamagnetic
• D. dielectric

Explanation: Diamagnetic materials have relative permeability slightly below unity, so they conduct magnetic flux slightly less readily than air.

• A. permanent magnets
• B. transformers
• C. non-magnetic substances
• D. electromagnets

Explanation: Retentivity is the ability to retain magnetism after the magnetising field is removed, which is essential for permanent magnets.

• A. attracts some substances and repels others
• B. attracts all paramagnetic substances and repels others
• C. attracts only ferromagnetic substances
• D. attracts ferromagnetic substances and repels all others

Explanation: A permanent magnet attracts magnetic substances such as iron and can repel another magnet when like poles face each other.

• A. diamagnetic
• B. paramagnetic
• C. ferromagnetic
• D. insulating

Explanation: Ferromagnetic materials have a strongly field-dependent permeability because their magnetic domains align and later become nonlinear or…

• A. loud-speakers
• B. generators
• C. motors
• D. all of the above

Explanation: Temporary magnets are electromagnets whose magnetism exists mainly while current flows, making them useful in loudspeakers, generators…

• A. strong tendency of fan out of laminations at the end caused by repulsion among magnetic lines of force
• B. uneven bearing surface, caused by dirt or uneven wear between moving and stationary parts
• C. both of above
• D. none of the above

Explanation: Solenoid noise can result from magnetic pull and repulsion that make laminations fan out, or from uneven bearing surfaces caused by dirt…

• A. by means of a small auxiliary motor
• B. from AC. side as induction motor
• C. from D.C. side as D.C. motor
• D. any of the above methods
• E. none of the above methodsHire Civil Engineers

Explanation: A synchronous converter has no inherent starting torque, so it may be brought up to speed by an auxiliary motor or started through its AC…

• A. two
• B. three
• C. four
• D. six
• E. noneTry Prep Courses

Explanation: A single-phase rotary converter receives single-phase AC through two slip rings, while its commutator supplies DC.

• A. an induction motor and a D.C. generator
• B. a synchronous motor and a D.C. generator
• C. a D.C. series motor and a D.C. generator
• D. none of the aboveCompare Home Electronics

Explanation: A rotary converter is essentially a synchronous motor and a DC generator combined on one armature and shaft.

• A. Motor generator set
• B. Motor converter
• C. Rotary converter
• D. Any of the above
• E. None of the above

Explanation: A rotary converter can work in reverse, accepting DC through its commutator and delivering AC through its slip rings.