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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 radiation of energy ‘E’ falls normally on a perfectly reflecting surface
- Angle of minimum deviation for a prism of reractive index 1.5 equal to the angle
- A ship of mass 3 x 10⁷ kg initially at rest is pulled by a force of 5 x 10⁴ N through
- A wheel has angular acceleration of 3.0 rad/sec² and an initial angular speed of 2.00
- Which one of the following electrical meter has the smallest resistance?
Topics: Current Electricity (136)
Subject: Physics (2479)
Important MCQs Based on Medical Entrance Examinations To Improve Your NEET Score
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