Understanding Electrostatic Potential Energy

Q. Work done by the field of fixed static charges on a 50mC charge is -20 J, as the charge moves from point A to point B slowly. The work done by the external agent is?

1. 20 J
2. -20 J
3. Zero
4. 100 mJ

Q. The displacement of a charge Q in the electric field $E=e_1\hat{i}+e_2\hat{j}+e_3\hat{k}$ is $\hat{r}=a\hat{i}+b\hat{j}$. The work done is

1. $Q(a{e}_1+b{e}_2)$
2. $Q\sqrt{(a{e}_1{)}^2+(b{e}_2{)}^2}$
3. $Q(e_1+e_2)\sqrt{a^2+b^2}$
4. $Q\left(\sqrt{e_1^2+e_2^2}\right)(a+b)$

Q.

Change in Potential energy is a __________ quantity.

1. Scalar

2. Vector

Q. Charges $q_1$ and $q_2$, 1C each are at infinite distance from each other initially. They are then brought to 1m distance in vacuum. What was the initial potential energy of the system?

1. $0$
2. $9\times {10}^9$
3. $-9\times {10}^9$
4. None of these.

Q.

A particle of mass m and charge q is released from rest in a uniform electric field E. The kinetic energy attained by the particle after moving a distance x along the electric field is

1. $qE{x}^2$

2. $q{E}^{2}x$

3. $qEx$

4. $q^{2}Ex$

Q. Charges $q_1$ and $q_2$, 1C each are at infinite distance from each other initially. They are then brought to 1m distance in vacuum. What was the initial potential energy of the system?

1. $0$
2. $9\times {10}^9$
3. $-9\times {10}^9$
4. None of these.

Q. Electric force on a point charge ‘q’ moving from point A to B is given by $\overrightarrow{F}=4i-8j$. What is the work done by this force if the vector joining A & B is given by $\overrightarrow{AB}=-4i$.

1. -4i + 8j
2. -16i + 32j
3. i – 2j
4. None of these

Q. Electric force on a point charge ‘q’ moving from point A to B is given by $\overrightarrow{F}=4i-8j$. What is the work done by this force if the vector joining A & B is given by $\overrightarrow{AB}=-4i$.

1. -4i + 8j
2. -16i + 32j
3. i – 2j
4. None of these