Electric charges are distributed in a small volume. The flux of the electric field through a spherical surface of radius \(10~\mathrm{cm}\) surrounding the total charge is \(25\) V-m. The flux over a concentric sphere of radius \(20\) cm will be:
1. \(25\) V-m
2. \(50\) V-m
3. \(100\) V-m
4. \(200\) V-m

The figure(a) shows an imaginary cube of edge \(L/2\). A uniformly charged rod of length \(L\) moves towards left at a small but constant speed \(u\). At \(t=0\), the left end just touches the centre of the face of the cube opposite it. Which of the graphs shown in figure(b) represents the flux of the electric field through the cube as the rod goes through it?

     
1. a
2. b
3. c
4. d

Given below are four statements:

Choose the correct option:

If the flux of the electric field through a closed surface is zero,

(a) the electric field must be zero everywhere on the surface

(b) the electric field may be zero everywhere on the surface

(c) the charge inside the surface must be zero

(d) the charge in the vicinity of the surface must be zero.

Choose the correct option 

1. (a) , (b) 

2. (b) , (c) 

3. (d) only

4. (a) , (d) 

(a) A
(b) B
(c) C
(d) D

Choose the correct option 

1. (a), (c)

2. (b), (c)

3. (d) only

4. (a), (d)

(a) is increased
(b) is decreased
(c) remains unchanged
(d) remains zero

Choose the correct option 

1. (a), (b) 

2. (b), (c) 

3. (d) only

4. (c), (d) 

The figure shows a closed surface which intersects a conducting sphere. If a positive charged is placed at the point P, the flux of the electric field through the closed surface

(a) will remain zero
(b) will become positive
(c) will become negative
(d) will become undefined

Choose the correct option 

1. (a), (b) 

2. (b), (c) 

3. (b) only

4. (a), (d)