Understanding Electrostatic Potential Energy

Q. Electric potential of earth is taken to be zero because earth is a good

1. Insulator
2. Conductor
3. Semiconductor
4. Dielectric

Q. Four particles of mass 1 kg, 2 kg, 2 kg, 3 kg are kept at points A, B, C, D respectively. (All coordinates are in metres)

Choose the correct option(s) regarding the position coordinates (x, y) of the system’s centre of mass.
द्रव्यमान 1 kg, 2 kg, 2 kg, 3 kg के चार कणों को बिन्दुओं क्रमशः A, B, C, D पर रखा गया है। (सभी निर्देशांक मीटर में हैं)
निकाय के द्रव्यमान केन्द्र के स्थिति निर्देशांकों (x, y) के संदर्भ में सही विकल्प/विकल्पों का चयन कीजिए।

1. x = 1.25 m
2. x = 1 m
3. y = 1 m
4. y = 1.25 m

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. When a +ve q charge is taken from lower potential to a higher potential point, then its PE will

1. Decrease
2. Increases
3. Remain unchanged
4. Become zero

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. Assertion :Nowadays a standard metre is defined as in terms of the speed of light. Reason: Light has no relation with length

1. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
2. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
3. Assertion is correct but Reason is incorrect
4. Assertion is incorrect but Reason is correct

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. $q^{2}Ex$