Question

An electron in potentiometer wire experiences a force of $2.4\times {10}^{-19}$N. The length of potentiometer wire is $6$m. 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

Given data,

$Force\left(F\right)=2.4\times {10}^{-19}$N

$Electroniccharge\left(e\right)=1.6\times {10}^{-19}$

$length\left(l\right)=6m$

$Volt\left(V\right)=?$

Let the emf be $V$ volts.

The electric field for a uniform potential drop is given by $E=\frac{V}{l}$ and force experienced by electron is given by $F=eE$.

Thus, substituting the values, we get, $V=\frac{Fl}{e}=\frac{2.4\times {10}^{-19}\times 6}{1.6\times {10}^{-19}}=9$ volts