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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
- 4.0 g of a gas occupies 22.4 litres at NTP. The specific heat capacity of the gas
- Which pair is isotonic?
- Two point charge +9e and +e are at 16 cm away from each other.
- Photons of energy 6 eV are incident on a metal surface whose work function is 4 eV.
- A shell of mass 200 g is ejected from a gun of mass 4 kg by an explosion
Topics: Current Electricity (136)
Subject: Physics (2479)
Important MCQs Based on Medical Entrance Examinations To Improve Your NEET Score
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