Question

An electron in potentiometer wire experiences a force $2.4\times {10}^{-19}$N. The length of potentiometer wire is $6m$. The e.m.f. of the battery connected across the wire is (electronic charge $=1.6\times {10}^{-19}$C).

• A. $6$V
• B. $9$V
• C. $12$V
• D. $15$V

Answer 1

The correct option is B $9$V

Electric field in the wire $E=\frac{F}{e}$

$\therefore$ $E=\frac{2.4\times {10}^{-19}}{1.6\times {10}^{-19}}=1.5$ $N/C$

Length of the wire $l=6$ m

Thus e.m.f of the battery $E=El$

$\therefore$ $E=1.5\times 6=9$ V