All Free Electrical Engineering MCQs with Answers

• A. 0.2 to 0.5 per cent
• B. 2 to 5 per cent
• C. 12 to 15 per cent
• D. 20 to 30 per cent

Explanation: Transformer no-load current is normally only about 2 to 5 percent of full-load current, although it can vary with transformer size and…

• A. tightness of clamping
• B. gauge of laminations
• C. size of laminations
• D. all of the above

Explanation: Transformer lamination vibration is affected by clamping tightness, lamination thickness or gauge, and lamination size.

• A. reduce hysteresis loss
• B. reduce eddy current losses
• C. reduce copper losses
• D. reduce all above losses

Explanation: Thin insulated laminations interrupt the circulating paths in the iron core, thereby reducing eddy-current loss.

• A. through cooling coil
• B. through air
• C. by the flux
• D. none of the above

Explanation: The alternating primary current produces magnetic flux in the core, and changing mutual flux induces the secondary voltage, transferring…

• A. Current
• B. Voltage
• C. Frequency
• D. All of the above

Explanation: A transformer changes voltage and current according to its turns ratio, but it operates at the same frequency as the applied supply.

• A. Input power
• B. Losses
• C. True component of power
• D. kWh consumed
• E. Ratio of output to input

Explanation: Efficiency is output power divided by input power, so reducing losses allows a larger fraction of the input to appear as useful output.

• A. 1.5.
• B. 0.5.
• C. 1.0.
• D. 1.2.

Explanation: Here SCR means short-circuit ratio, not silicon-controlled rectifier. Modern alternators commonly have a short-circuit ratio of about 0.5…

• A. Cost
• B. Durability
• C. Compliance with performance criteria as laid down in specifications
• D. All of the above

Explanation: A sound design must satisfy the specified performance requirements while also being economical and sufficiently durable.

• A. paper mills
• B. steel mills
• C. moist atmospheres
• D. explosive atmospheres

Explanation: Flame-proof motors are enclosed so that any internal spark or flame does not ignite the surrounding atmosphere.

• A. A mechanical
• B. An electronic
• C. An electromechanical
• D. None of the above

Explanation: A relay combines an electrical coil with mechanically moving contacts, so it is classified as an electromechanical switch.

• A. smoky and dirty atmosphere
• B. humidity in the atmosphere
• C. both (A) and (b)
• D. neither (A) nor (b)

Explanation: Moisture forms a partially conducting film on an insulator, while smoke and dirt provide or retain contaminating conductive paths.

• A. Aluminium is more ductile and malleable than copper
• B. Aluminium is available in plenty, cheaper and lighter than copper
• C. Aluminium has lower resistivity than that of copper
• D. Aluminium has less temperature co-efficient than copper

Explanation: Aluminium is widely used instead of copper because it is more abundant, cheaper, and much lighter, although its resistivity is higher.

• A. Porcelain
• B. Slate
• C. Asbestos
• D. Glass

Explanation: Spark plugs use porcelain as the insulator because it withstands high temperature, high voltage, and chemical attack inside an engine.

• A. Both have great tendency for oxidation
• B. Both have low melting point
• C. Very large length of wires will be required
• D. All of the above

Explanation: Copper and aluminium have low resistivity, so impractically long wires would be needed to obtain the resistance required for heating; they…

• A. Tungsten
• B. Aluminium
• C. Copper
• D. Carbon

Explanation: Among the listed materials, copper has the lowest resistivity and therefore the highest electrical conductivity.

• A. Less liability to kink
• B. Greater flexibility
• C. Less liability to break
• D. All of the above

Explanation: Stranding makes a conductor more flexible, reduces its tendency to kink, and allows it to withstand repeated bending without breaking as…

• A. transformer, motor and generator windings
• B. transmission and distribution lines
• C. house wiring
• D. all above applications

Explanation: Low-resistivity conductors reduce I²R losses and voltage drop, so they are used in machine windings, transmission and distribution lines…

• A. Kanthal
• B. Manganin
• C. Nichrome
• D. Eureka

Explanation: Kanthal is an iron-chromium-aluminium resistance alloy capable of operating at very high temperatures, generally higher than Nichrome…

• A. a ceramic body having metal and caps
• B. a wire of platinum
• C. a heavy cross-section of copper or aluminium
• D. a ceramic tube having carbon rod inside it

Explanation: An H.R.C. fuse has a heat-resistant ceramic body with metal end caps and a calibrated fuse element inside.

• A. maximum fault current carrying through the ground wire
• B. rated current carrying capacity of the service line
• C. depends on the soil resistance
• D. both (A) and (C)

Explanation: Grounding design must provide a safe path for the prospective fault current, while soil resistance affects how effectively the grounding…