A 40 W tube light consumes _____ energy in 8 hours. MCQ with Answer and Explanation

A 40 W tube light consumes _____ energy in 8 hours.
A. 0.04 kWh
B. 5 kWh
C. 320 kWh
D. 0.32 kWh
Answer: Option D
Solution (By JKSSB Mock Tests)
Energy = 0.04 kW × 8 h = 0.32 kWh.

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Practice More Physics Questions

Question #1
The time period of a simple pendulum is independent of:
A. Amplitude (for small angles)
B. Acceleration due to gravity
C. Mass of bob
D. Length of pendulum

Correct Answer: Option C


Explanation:
Pendulum period T = 2π√(l/g) for small amplitudes. It depends on length l and gravity g, but not on bob mass or amplitude (isochronism for small angles). Mass independence arises because gravitational force and inertia both proportional to mass, canceling out. Memory aid: 'Pendulum: T ∝ √(l/g); independent of mass and small-amplitude'. This conceptual question tests oscillations fundamentals, frequently examined in competitive exams. Always verify the small-angle approximation; competitive exams assume it unless specified otherwise. This problem assesses understanding of which parameters affect periodic motion.

This question belongs to: Science Physics
Question #2
In the equation F = ma, if mass is doubled and acceleration is halved, force becomes
A. Double
B. Four times
C. Half
D. Same

Correct Answer: Option D


Explanation:
F = m×a. New force F' = (2m)×(a/2) = m×a = F. So force remains unchanged. This is direct proportionality. Understand the relationship: doubling mass doubles force, halving acceleration halves it, net effect no change.

This question belongs to: Science Physics
Question #3
The magnetic field inside a long straight solenoid is
A. Strong at ends and weak in middle
B. Inversely proportional to current
C. Zero
D. Uniform

Correct Answer: Option D


Explanation:
Ideal solenoid interior has uniform magnetic field B = μ₀ n I, parallel to axis. Outside field weak. Used in electromagnets, relays. Uniformity for scientific instruments.

This question belongs to: Science Physics