Moving Charges and Magnetism — Physics STD 12 Science — Question

Two protons are kept at a separation of 10nm. Let F_n and F_e be the nuclear force and the electromagnetic force between them:

1. F_e = F_n.
   
2. F_e >> F_n.
   
3. F_e << F_n.
   
4. F_e and F_n differ only slightly.
   

If the current is halved in a coil, then the energy stored is how much times the previous value

(a)

(b)

(c) 2

(d) 4

What happens when negative terminal of cell is connected to other negative terminal of cell in a particular circuit?

The distance between the plates of a parallel plate condenser is 8mm and P.D. 120 volts. If a 6mm thick slab of dielectric constant 6 is introduced between its plates, then

(a) The charge on the condenser will be doubled

(b) The charge on the condenser will be reduced to half

(c) The P.D. across the condenser will be 320 volts

(d) The P.D. across the condenser will be 45 volts

The atomic number and mass number for a specimen are Z and A respectively. The number of neutrons in the atom will be :

Which one of the following properties of an element is not variable?

Which of the following formula is correct for a spherical lens?

An infinitely long cylinder is kept parallel to an uniform magnetic field B directed along positive z axis. The direction of induced current as seen from the z axis will be

(a)  Clockwise of the +ve z axis	(b) Anticlockwise of the +ve z axis
(c) Zero	(d) Along the magnetic field

Assertion  :   The surface charge densities of two spherical conductors of different radii are equal. Then the electric field intensities near their surface are also equal.

Reason    : Surface charge density is equal to charge per unit area.

(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.

(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.

(c) If assertion is true but reason is false.

(d) If the assertion and reason both are false.