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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
- A photon of energy 10.2 eV collide inelastically with hydrogen atom in ground state
- Two tuning forks are sounded together and produce 2 beats per second.
- An electron in the hydrogen atom jumps from excited state n to the ground state
- A particle moves along the x-axis such that its co-ordinate (x) varies with time (t)
- A body initially at rest is moving with uniform acceleration a m/s²
Topics: Current Electricity (136)
Subject: Physics (2479)
Important MCQs Based on Medical Entrance Examinations To Improve Your NEET Score
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