# The length of a Potentiometer wire is 5 metres. An electron in this wire experiences a force…

Q: The length of a Potentiometer wire is 5 metres. An electron in this wire experiences a force of 4.8 × 10-19 N , e.m.f. of the main cell used in Potentiometer is :

(a) 3 volt

(b) 15 volt

(c) 1.5 volt

(d) 5 volt

Ans: (b)

Sol: Force = electric intensity × charge

$\displaystyle Force = \frac{Potential \; difference }{distance} \times charge$

$\displaystyle 4.8 \times 10^{-19} = \frac{V}{5} \times 1.6 \times 10^{-19}$

V = 15 volt