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======= ####70. Ten identical cells connected in series are needed to heat a wire of length one meter and radius ’ $r$ ’ by $10^{\circ} C$ 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 ’ $t$ ‘?

c3eec34ec6b1fad69db54a20ad4b2dca40c2aa54 (a) 10

(b) 20

(d) 40

[NEET Kar. 2013]

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Answer:

Correct Answer: 70. (b)

Solution:

(b) Resistance is directly proportionl to length of the wire. As length is doubled so mass is doubled and resistance is doubled.

We have

$\frac{(10 E)^{2}}{R} t = m S Δ T$ , Now $\frac{(n E)^{2} t}{2 R} = (2 m) S Δ T$

$\Rightarrow \frac{n^{2} E^{2} t}{2 R} = 2 \frac{10^{2} E^{2} t}{R}$

$\Rightarrow n = 20$

Current Electricity - Result Question 65

70. Ten identical cells connected in series are needed to heat a wire of length one meter and radius ’ $r$ ’ by $10^{\circ} C$ 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 ’ $t$ ‘?

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Answer:

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Current Electricity - Result Question 65

70. Ten identical cells connected in series are needed to heat a wire of length one meter and radius ’ r ’ by 10∘C 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 ‘?

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Answer:

Engineering Preparation

Medical Preparation

NCERT Books & Solutions

Important Resources

Other Resources

Syllabus

Test Platform

Sample Mock Test

Mentorship

NCERT Exercise Video Solution

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70. Ten identical cells connected in series are needed to heat a wire of length one meter and radius ’ $r$ ’ by $10^{\circ} C$ 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 ’ $t$ ‘?