NEET Physics Current Electricity Questions Solved

A wire of radius r has resistance R. If it is stretched to a radius of $\frac{3 r}{4}$ , its resistance becomes

(1) $\frac{9 R}{16}$

(2) $\frac{16 R}{9}$

(3) $\frac{81 R}{256}$

(4) $\frac{256 R}{81}$

(4) $\frac{R_{1}}{R_{2}} = {(\frac{r_{2}}{r_{1}})}^{4}$

⇒ $\frac{R}{R_{2}} = {(\frac{3 r / 4}{r})}^{4} = \frac{81}{256} = R_{2} = \frac{256}{81} R$

Difficulty Level:

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