Question

The resistance of a wire is 10 $\Omega$. Its length increased by 10% by stretching. The new resistance will now be

• A. $12\Omega$
• B. $1.2\Omega$
• C. $13\Omega$
• D. $11\Omega$

Answer 1

Answer: (A)

$12\Omega$

we know $R=\frac{\rho l}{A}$

since volume is constant $r^{2}l=constant$

If length is increased by $10\%$

$l\to 1.1l$

$r^2\to r^2/1.1$

$R\to {1.1}^{2}R$

$R=(1.1{)}^2\times 10=12\Omega$