Electric motor works on principle of: MCQ with Answer and Explanation

Electric motor works on principle of:
A. Thermal expansion
B. Electromagnetic induction
C. Force on current in magnetic field
D. Electrostatic attraction
Answer: Option C
Solution (By JKSSB Mock Tests)
Motor: current-carrying conductor in magnetic field experiences Lorentz force (F = ILB), causing rotation. Generator uses reverse principle (induction). Memory tip: 'Motor: electricity ⇒ motion (force); Generator: motion ⇒ electricity (induction)'. Device principle question frequently tested in competitive electromagnetism sections.

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Question #1
Which of the following is a good insulator?
A. Copper
B. Rubber
C. Graphite
D. Silver

Correct Answer: Option B


Explanation:
Rubber has no free electrons, high resistivity. Silver best conductor. Copper widely used conductor. Graphite conducts (non-metal). Insulators: glass, plastic, wood.

This question belongs to: Science Physics
Question #2
The property of a body to resist change in its state of motion is called
A. Inertia
B. Force
C. Momentum
D. Weight

Correct Answer: Option A


Explanation:
Inertia is directly proportional to mass. Heavier object harder to accelerate/decelerate. Newton's first law defines inertia. Momentum is mass × velocity, depends on motion.

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Question #3
A simple pendulum is taken to moon. Its time period
A. Increases
B. Remains same
C. Becomes zero
D. Decreases

Correct Answer: Option A


Explanation:
T ∝ 1/√g, g_moon < g_earth, so T increases.

This question belongs to: Science Physics