The working of an electric motor is based on MCQ with Answer and Explanation

The working of an electric motor is based on
A. Electromagnetic induction
B. Heating effect of current
C. Chemical effect of current
D. Magnetic effect of current
Answer: Option D
Solution (By JKExamLibrary)
Motor converts electrical to mechanical energy using force on a current-carrying conductor in magnetic field (F = BIL). Electromagnetic induction is for generator. Motor principle: A current-carrying coil experiences torque in magnetic field.

This question belongs to: Science Physics

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Question #1 Report Error
The device used to convert solar energy into electrical energy is
A. Solar cell
B. Solar heater
C. Battery
D. Wind turbine

Correct Answer: Option A


Explanation:
Photovoltaic cell (solar cell) directly converts sunlight to electricity. Solar heater uses sun to heat water, not electricity. Wind turbine converts wind energy. Battery stores chemical energy.

This question belongs to: Science Physics
Question #2 Report Error
A electric iron of 500 W is used for 2 hours. Energy consumed in kWh is
A. 1 kWh
B. 0.5 kWh
C. 250 kWh
D. 1000 kWh

Correct Answer: Option A


Explanation:
0.5 kW × 2 h = 1 kWh.

This question belongs to: Science Physics
Question #3 Report Error
The escape velocity from a planet depends on:
A. Radius of the planet only
B. Mass of the escaping body
C. Temperature of the planet
D. Both mass and radius of the planet

Correct Answer: Option D


Explanation:
Escape velocity v_e = √(2GM/R), where M is planet mass, R its radius. Thus v_e depends on both M and R. It is independent of the escaping body's mass (as gravitational and inertial mass cancel). Memory tip: 'v_e ∝ √(M/R); larger M or smaller R ⇒ higher escape velocity'. This gravitation formula application is frequently tested in competitive exams. Always recall that escape velocity is a property of the planet, not the projectile. This problem assesses understanding of gravitational potential energy concepts.

This question belongs to: Science Physics