A) 1.2 times, 1.1 times
B) 1.21 times, same
C) both remain the same
D) 1.1 times, 1.1 times
Correct Answer: B
Solution :
| [b] Key Idea: In stretching, specific resistance remains unchanged. |
| After stretching, specific resistance (p) will remain same. |
| Original resistance of the wire, \[R=\frac{\rho l}{A}\] |
| or \[R\propto \frac{l}{A}\] |
| or \[R\propto \frac{{{l}^{2}}}{V}\] \[(\text{as}\,\,\,V=Al)\] |
| and \[R'\propto \frac{{{(l+10%l)}^{2}}}{V}\] |
| Therefore, \[\frac{R'}{R}=\frac{{{\left( l+\frac{10}{100}l \right)}^{2}}}{{{l}^{2}}}\] |
| or \[\frac{R'}{R}=\frac{{{\left( \frac{11l}{10} \right)}^{2}}}{{{l}^{2}}}=\frac{121}{100}\] |
| or \[R'=1.21\,R\] |
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