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The identical cells connected in series are needed to heat a wire of length one meter and radius ‘r’ by 10⁰C in time ‘t’. How many cells will be required to heat the wire of length two meter of the same radius by the same temperature in time ‘t’?
Options
(a) 10
(b) 20
(c) 30
(d) 40
Correct Answer:
20
Explanation:
Resistance is directly proportional to length of the wire. As length is doubled so mass is doubled and resistance is doubled. We have
(10 E)² / R . t = mS∆T,
Now, (nE)²t / 2R = (2m) S∆T
⇒ n²E²t / 2R = 2 . 10²E²t / R
⇒ n = 20
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Topics: Current Electricity
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Subject: Physics
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Important MCQs Based on Medical Entrance Examinations To Improve Your NEET Score
- A car moving with a speed of 50 kmh⁻¹ can be stopped by brakes after at least 6 m
- In the relation n=PV/RT, n stands for
- In the spectrum of hydrogen, the ratio of the longest wavelength in the Lyman series
- Sound waves travel at 350m/s through a warm air and at 3500 m/s through brass
- A charged particle with a velocity 2×10³ ms⁻¹ passes undeflected through electric field
Topics: Current Electricity (136)
Subject: Physics (2479)
Important MCQs Based on Medical Entrance Examinations To Improve Your NEET Score
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