Question

Two points P and Q are maintained at potentials of of $10V$ and $-4V$ respectively. The work done in moving $100$ electrons from P to Q is equal to

• A. $2.24\times {10}^{-16}J$
• B. $-9.6\times {10}^{-17}J$
• C. $-2.24\times {10}^{-16}J$
• D. $9.6\times {10}^{-17}J$

Answer 1

The correct option is A $2.24\times {10}^{-16}J$

$\text{Step 1: Work done by external agent}$

As only work done is mentioned in the problem, that means Work done by external agent is asked, $W_{ext}=q\Delta V$

Now

$\Delta V=V_Q-V_P=(-4-10)V=-14V$

$q=N.e=100\times (-1.6\times {10}^{-19}C)$

$=-1.6\times {10}^{-17}C$

Therefore, Work done due to external agent$\left(W\right)=q\Delta V$

$=-1.6\times {10}^{-17}\times (-14)=2.24\times {10}^{-16}J$

Hence, Option $A$ is correct.