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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 name of ions knocked out from the hot surface is
- An electric motor runs on DC source of emf 200 V and draws a current of 10 A.
- A block slides from an inclination of 45°.If it takes time twice
- Dimensions formula for surface tension is
- Two cities are 150 km apart. Electric power is sent from one city to another city
Topics: Current Electricity (136)
Subject: Physics (2479)
Important MCQs Based on Medical Entrance Examinations To Improve Your NEET Score
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