Question

A wire is 10m long and reseistance of wire is 20ohm. A potential difference of 10^-5volt/cm is to be created along the length of the wire . Find the value of R needed if Es=1.082V and the galvanometer shows no deflection.

Answer 1

Gives

Length (l)=10 m

Resistance (R)=20 ohm

Potential difference (V)=$10^{-3} V/m$

Es=1.082V

R'=?

We know that V=IR

Current (I)=$\frac{10^{-3}}{20}=5\times10^{-5}A$

Then we know that

$E_s=\frac{I(R'+R)}{l}$

Put value

$1.082=\frac{5\times10^{-5}\times(R'+20)}{10}$

R'=216380 ohm

R'=0.22$M\Omega$