Question

The potential at a point due to a charge of $5\times {10}^{-7}C$ located $10cm$ away is $4.5\times {10}^{4}V$. The work done in bringing a charge of $4\times {10}^{-9}C$ from infinity to that point is:

• A. $2.4\times {10}^{-4}J$
• B. $1.8\times {10}^{-4}J$
• C. $3.2\times {10}^{-5}J$
• D. $4.1\times {10}^{-5}J$

Answer 1

Answer: (B)

$1.8\times {10}^{-4}J$

Work done $W=q(V_f-V_i)=4\times {10}^{-9}\times 4.5\times {10}^4=1.8\times {10}^{-4}J$