Electron e/m measured by: MCQ with Answer and Explanation

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Electron e/m measured by:

A. Thomson

B. Millikan

C. Bohr

D. Rutherford

Answer: Option A

Solution (By JKSSB Mock Tests)

J.J. Thomson measured e/m using cathode ray deflection (1897). Millikan later measured e (oil drop). Memory aid: 'Thomson = e/m; Millikan = e'. Experimental physics history frequently tested in competitive exams.

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Question #1

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The instrument used to measure potential difference is

A. Voltmeter

B. Ohmmeter

C. Ammeter

D. Galvanometer

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Correct Answer: Option A

Explanation:
Voltmeter measures potential difference in volts. Connected in parallel. Ideal voltmeter has infinite resistance. Galvanometer can be converted to voltmeter by adding high resistance in series.

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Question #2

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Gravity work for horizontal motion:

A. Zero

B. Speed dependent

C. Negative

D. Positive

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Correct Answer: Option A

Explanation:
Gravity acts vertically; horizontal displacement ⇒ angle = 90° ⇒ W = Fd cos90° = 0. No work for perpendicular force-displacement. Memory aid: 'Work = Fd cosθ; θ=90° ⇒ W=0'. Mechanics concept frequently tested to correct misconception that force always does work.

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