Electric Field

Q.

A charged particle of mass 1.0 g is suspended through a silk thread of length 40 cm in a horizontal electric field of intensity $4.0\times {10}^{4}N{C}^{-1}$ as shown in the figure. If the particle stays in equilibrium at a distance of 24 cm from the wall, find the net charge on the particle?

1. q = 1.8 × 10^–7 C

2. q = 3.2× 10^–7 C

3. None of these

4. q = –3.2× 10^–7 C

Q.

An electron is fixed at the origin as shown. What is the electric field at A?

1. $3.6\times {10}^{-19}\text{N/C}\hat{i}$
2. $-3.6\times {10}^{-10}\text{N/C}\hat{i}$
3. $3.6\times {10}^{-10}\text{N/C}\hat{i}$
4. None of these

Q.

One can add electric field and gravitational field.

1. True

2. False

Q.

The electric charge in uniform motion produces

1. Neither electric nor magnetic field

2. Both electric and magnetic field

3. An electric field only

4. A magnetic field only

Q.

[CPMT 1990]

1. Cannot be estimated

2. 
   

3. 
   

4. 
   

Q.

In the absence of other conductors, the surface charge density

1. Is proportional to the charge on the conductor and its surface area

2. Inversely proportional to the charge and directly proportional to the surface area

3. Directly proportional to the charge and inversely proportional to the surface area

4. Inversely proportional to the charge and the surface area

Q.

A point charge produces an electric field of magnitude 5.0 $N{C}^{-1}$ at a distance of 40 cm from it. What is the magnitude of charge?

1. $8.9\text{C}$

2. $-8.9\times {10}^{11}\text{C}$

3. $8.9\times {10}^{-11}\text{C}$

4. ${10}^{-11}\text{C}$

Q. A particle of mass $m$ and charge $-q$ is projected from the origin with a horizontal speed $v$ into a space having electric field of magnitude $E$ directed downwards as shown in the figure. If the effect due to gravity can be neglected, then choose the correct statement(s) among the following.

1. The equation of trajectory is $y=\frac{1}{2}\left(\frac{qE{x}^2}{m{v}^2}\right)$
2. The kinetic energy after a displacement $y$ is $qEy$
3. The horizontal and vertical displacements $x$ and $y$ after a time $t$ are $x=vt$ and $y=\frac{1}{2}{a}_y{t}^2$
4. The horizontal and vertical components of acceleration are $a_x=0,a_y=\frac{qE}{m}$

Q.

Find electric field at point (2, 1) due to an electron placed at the origin

1. 

2. 

3. 

4. 

Q.

A charged water droplet hangs from ceiling of a room which has a uniform vertically upwards electrical field of strength 4.00 $\times {10}^{5}N{C}^{-1}$ . This field levitates and prevents a droplet of mass 1.0 $\times {10}^{-4}$kg from falling. Can you find the net charge on the droplet?

1. 4.00 × 10^–9 C

2. 2.45 × 10^–9 C

3. 5.40 × 10^–9 C

4. 1.75 × 10^–9 C