MCQ
A thick wire is stretched so that its length become two times. Assuming that there is no change in its density, then what is the ratio of change in resistance of wire to the initial resistance of wire
- A$2: 1$
- B$4: 1$
- ✓$3: 1$
- D$1: 4$
✓
Answer
Correct option: C.
$3: 1$
(c) In stretching $R \propto l^2 \Rightarrow \frac{R_2}{R_1}=\frac{l_2^2}{l_1{ }^2} \Rightarrow \frac{R_2}{R_1}=\left(\frac{2}{1}\right)^2$$\Rightarrow R_2=4 R_1$. Change in resistance $=R_2-R_1=3 R_1$Now, $\frac{\text { Change in resistance }}{\text { Original resistance }}=\frac{3 R_1}{R_1}=\frac{3}{1}$
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