A 10 m long wire of uniform cross-section and 20`Omega` resistance is used in a potentiometer. The wire is connected in series with a battery of 5 V along with an external resistance of 480 2. If an unknown emf E is balanced at 6.0 m length of the wire, calculate (i) the potential gradient of the potentiometer wire, (ii) the value of unknown emf.

Explanation

Here resistance of potentiometer wire `r = 20 Omega , epsi 5V , R = 480 Omega " and " L = 10 m`
` therefore ` Potential gradient of the potentiometer wire
`k = ((epsi.r)/((R+r)).L)`
` = (5 xx 20)/((480 + 20) xx 10)`
`= 2 xx 10^(-2) V//m`
(ii) Value of unknown emf `E = kl = 2 xx 10^(-2) xx 6 = 0.12 V`