A 60 W bulb operates at 120 V. Its resistance is MCQ with Answer and Explanation

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A 60 W bulb operates at 120 V. Its resistance is

A. 120 Ω

B. 480 Ω

C. 240 Ω

D. 60 Ω

Answer: Option C

Solution (By JKExamLibrary)

R = V²/P = 14400/60 = 240 Ω.

This question belongs to: Science Physics

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Question #1 Report Error

If the random error in measurement of radius of a sphere is 2%, the error in volume is

A. 2%

B. 8%

C. 6%

D. 4%

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Correct Answer: Option C

Explanation:
Volume V = (4/3)πr³. Fractional error ΔV/V = 3 Δr/r. Percentage error = 3 × 2% = 6%. Important for error analysis in competitive exams.

This question belongs to: Science Physics

Question #2 Report Error

Heat transfer in liquids and gases mainly occurs by

A. Conduction

B. Radiation

C. Convection

D. Sublimation

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Correct Answer: Option C

Explanation:
Convection: movement of fluid due to density differences caused by temperature. Hot fluid rises, cold sinks, creating currents. Land/sea breeze, trade winds. Conduction in solids primarily.

This question belongs to: Science Physics

Question #3 Report Error

A transformer has 50 turns in the primary coil and 1000 turns in the secondary coil. If the primary voltage is 220V, what is the secondary voltage?

A. 440 V

B. 4400 V

C. 22000 V

D. 11 V

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Correct Answer: Option B

Explanation:
The transformer equation relates voltages to the number of turns: V_secondary / V_primary = N_secondary / N_primary. We have N_p = 50, N_s = 1000, and V_p = 220V. Substituting the values gives V_s / 220 = 1000 / 50. V_s = 220 * 20 = 4400 Volts. This is a step-up transformer, increasing the voltage strictly by a factor of 20.

This question belongs to: Science Physics

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