Question

A uniform metallic wire carries a current $2 A$, when $34 V$ battery is connected across it The mass of uniform metallic wire is $892 \times 10^{-3} kg$, density is $892 \times 10^3 kg / m ^3$ and resistivity is $17 \times 10^{-8} \Omega- m$ The length of wire is :

• A. $l=10\, m$
• B. $l=100\, m$
• C. $l=5\, m$
• D. $l=6.8 \, m$

Answer 1

The Correct Option is A

$I=2A$
$\Delta V=3.4V$
Using Ohm's Law $R=\frac{3.4}{2}=1.7\Omega$
$1.7=\frac{\rho L}{A}$
$L=\frac{1.7(A)}{\rho }$
$M=$ ( density volume )
Volume $=\frac{8.92\times 10^{-3}}{8.92\times 10^3}=10^{-6}$
$L^2=\frac{1.7}{\rho }\left(10^{-6}\right)=\frac{1.7}{1.7}\times 10^2$
$L=10m$