Verified Solution • 2025–26 Session moderate

QJEEM22Phbaca: JEE Main 2022 Physics - Class 12 JEEM22Phbaca Solution: A wire of resistance R 1 is drawn out so that its length is…

A wire of resistance R₁ is drawn out so that its length is increased by twice of its original length. The ratio of new resistance to original resistance is :

Multiple Choice Options

A 9:01
B 1:09
C 4:01
D 3:01

Step-by-Step Verified Solution

Length is increased by twice of its original length.

So, if original length is

l_1

then final length is

l_2

l_1

+ 2

l_1

= 3

l_1

.

Then area becomes, A₂ =

\frac{A_{1}}{3}

\begin{aligned} R_{1} = \frac{p l_{1}}{A_{1}} \\ R_{2} = \frac{p l_{2}}{A_{2}} = \frac{p \times 3 l_{1}}{A_{1} / 3} = 9 \frac{p l_{1}}{A_{1}} = 9 R_{1} \\ ∴ R_{2} : R_{1} = 9 : 1 \end{aligned}

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