Question

Work done by external forces in moving a charge $q$ from $R$ to $P$ as shown in figure is

• A. $-\underset{R}{\overset{P}{\int }}{F}_E\cdot dr$
• B. $\underset{R}{\overset{P}{\int }}{F}_E\cdot dr$
• C. $\underset{R}{\overset{P}{\int }}2F_E\cdot dr$
• D. $\underset{R}{\overset{P}{\int }}\frac{F_E}{2}\cdot dr$

Answer 1

Answer: (A)

Thus, work done by external forces in moving a charge $q$ from $R$ to $P$ is
$W_{RP}=\underset{R}{\overset{P}{\int }}{F}_{ext}\cdot dr=-\underset{R}{\overset{P}{\int }}{F}_E\cdot dr$