Model Paper 2 — Physics STD 12 Science — Question

A particle moving in a magnetic field increases its velocity, then its radius of the circle

(a) Decreases

(b) Increases

(c) Remains the same

(d) Becomes half

There are  photons of frequency    in a beam of light. In an equally energetic beam, there are  photons of frequency . Then the correct relation is

(a)

(b)

(c)

(d)

Consider a sample of a pure beta-active material:

A mass m = 20 g  has a charge q = 30 mC. It moves with a velocity of 20 m/s  and enters a region of electric field of 80 N/C in the same direction as the velocity of the mass. The velocity of the mass after 3 seconds in this region is

(a) 80 m/s

(b) 56 m/s

(c) 44 m/s

(d) 40 m/s

The resolving power of a telescope depends on:

A circular loop of radius 0.0157m carries a current of 2.0 amp. The magnetic field at the centre of the loop is (

(a) 1.57	(b) 8.0
(c) 2.5	(d)  3.14

The ampere-sec stands for the unit of:

A metallic ring connected to a rod oscillates freely like a pendulum. If now a magnetic field is applied in horizontal direction so that the pendulum now swings through the field, the pendulum will

(a) Keep oscillating with the old time period

(b) Keep oscillating with a smaller time period

(c) Keep oscillating with a larger time period

(d) Come to rest very soon

In a nuclear reaction some mass converts into energy. In this reaction total B.E of reactants when compared with that of products is:

A convex lens

(a) Converges light rays	(b) Diverges light rays
(c) Form real images always	(d) Always forms virtual images