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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
(136)
Subject: Physics
(2479)
Important MCQs Based on Medical Entrance Examinations To Improve Your NEET Score
- The current in the windings of a toroid is 2.0 A. There are 400 turns
- The force F acting on a particle of mass m is indicated by the force-time graph
- The magnetic moment has dimensions of
- Electrons in a certain energy level n=n₁, can emit 3 spectral lines. When they
- An open knife edge of mass 200g is dropped from height 5m on a cardboard
Topics: Current Electricity (136)
Subject: Physics (2479)
Important MCQs Based on Medical Entrance Examinations To Improve Your NEET Score
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