A 100 W bulb is used for 10 hours. Energy consumed is MCQ with Answer and Explanation

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A 100 W bulb is used for 10 hours. Energy consumed is

A. 100 kWh

B. 1 kWh

C. 10 kWh

D. 0.1 kWh

Answer: Option B

Solution (By JKExamLibrary)

Energy = 0.1 kW × 10 h = 1 kWh.

This question belongs to: Science Physics

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Practice More Physics Questions

Question #1 Report Error

The focal length of a concave mirror is 15 cm. The radius of curvature is

A. 7.5 cm

B. 30 cm

C. 45 cm

D. 15 cm

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Correct Answer: Option B

Explanation:
For spherical mirrors, R = 2f. So R = 2 × 15 = 30 cm. Sign convention: for concave mirror, f and R are negative by Cartesian convention, but magnitude 30 cm. So 30 cm is correct.

This question belongs to: Science Physics

Question #2 Report Error

The scientist who discovered X-rays is

A. Becquerel

B. Rutherford

C. Roentgen

D. Curie

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Correct Answer: Option C

Explanation:
Wilhelm Roentgen discovered X-rays in 1895, won first Nobel in Physics.

This question belongs to: Science Physics

Question #3 Report Error

A light ray enters from air into glass. How does its speed, frequency, and wavelength change?

A. Speed remains same, frequency decreases, wavelength increases.

B. Speed decreases, frequency remains same, wavelength decreases.

C. Speed decreases, frequency decreases, wavelength decreases.

D. Speed increases, frequency remains same, wavelength increases.

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Correct Answer: Option B

Explanation:
When light passes from a rarer medium (air) to a denser medium (glass), its speed decreases due to the higher refractive index. Wavelength is directly proportional to speed, so it also decreases. However, the frequency depends only on the source of light and remains absolutely constant during refraction across any boundary.

This question belongs to: Science Physics

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