Electric Charges and Fields — Physics STD 12 Science — Question

Let V and E be the gravitational potential and gravitational field at a distance r from the centre of a uniform spherical shell. Consider the following two statements:

1. The plot of V against r is discontinuous.
2. The plot of E against r is discontinuous.

1. Both A and B are correct.
2. A is correct but B is wrong.
3. B is correct but A is wrong.
4. Both A and B are wrong.

Magnetic fields at two points on the axis of a circular coil at a distance of 0.05m and 0.2m from the centre are in the ratio 8 : 1. The radius of the coil is

(a) 1.0 m

(b) 0.1 m

(c) 0.15 m

(d) 0.2 m

Assertion :   Magnetic flux can produce induced e.m.f.

Reason     : Faraday established induced e.m.f. experimentally.

(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 assertion is false but reason is true.

A light source approaches the observer with velocity 0.8 c. The doppler shift for the light of wavelength  5500 Å is

(a) 4400 Å

(b) 1833 Å

(c) 3167 Å

(d) 7333 Å

If a dielectric introduced between the plates of a parallel plate condenser, then which of the following is possible:

Two long parallel wires P and Q are both perpendicular to the plane of the paper with distance 5 m between them. If P and Q carry current of 2.5 amp and 5 amp respectively in the same direction, then the magnetic field at a point half way between the wires is

(a)

(b)

(c)

(d)

Why high temperature is required for Nuclear fusion?

A wire in the form of a square of side ‘a’ carries a current i. Then the magnetic induction at the centre of the square wire is (Magnetic permeability of free space =

(a)

(b)

(c)

(d)