Question

The resistivity of a potential meter wire is if the area of cross section of the wire is $4c{m}^2$ . The current flowing in the circuit is 1A, the potential gradient is 7.5 v/m

• A. $3\times {10}^{-3}\Omega -m$
• B. $2\times {10}^{-6}\Omega -m$
• C. $4\times {10}^{-2}\Omega -m$
• D. $5\times {10}^{-4}\Omega -m$

Answer 1

The correct option is A $3\times {10}^{-3}\Omega -m$

We know that,

Potential gradient $V/l=7.5v/m$

Area of cross section $A=4c{m}^2=0.0004m^2$

Current flowing $I=1A$

Now, $\frac{V}{l}=\frac{PI}{a}7.5v/m=\frac{P\left(1A\right)}{0.0004}P=7.5\times 0.0004P=0.0030\Omega mP=3\times {10}^{-3}\Omega m$