Current Electricity — Physics STD 12 Science — Question

An electron moving with the speed 5   per sec is shooted parallel to the electric field of intensity 1 . Field is responsible for the retardation of motion of electron. Now evaluate the distance travelled by the electron before coming to rest for an instant (mass of e = 9 .  charge = 1.6 )

(a) 7 m

(b) 0.7 mm

(c) 7 cm

(d) 0.7 cm

Assertion  :   There is no atmosphere on moon

Reason      : Escape velocity at the surface of moon is low.

(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.

If the source of light used in a Young's double slit experiment is changed from red to violet:

1. The fringes will become brighter.
2. Consecutive fringes will come closer.
3. The intensity of minima will increase.
4. The central bright fringe will become a dark fringe.

Black hole is a

(a) Hole in the ozone layer of atmosphere

(b) Hole in earth's centre

(c) Highly dense matter available in the atmosphere

(d) Hole in troposphere

A capacitor of capacity C has charge Q  and stored energy is W. If the charge is increased to 2Q, the stored energy will be

(a) 2W

(b) W/2

(c) 4W

(d) W/4

The direction of electric field is from:

Consider a sample of a pure beta-active material:

1. All the beta particles emitted have the same energy.
2. The beta particles originally exist inside the nucleus and are ejected at the time of beta decay.
3. The antineutrino emitted in a beta decay has zero mass and hence zero momentum.
4. The active nucleus changes to one of its isobars after the beta decay.

The rate of disintegration was observed to be  disintegrations per sec when its half life period is 1445 years. The original number of particles are

(a) 8.9

(b) 6.6

(c) 1.4

(d) 1.2

The binding energy per nucleon is maximum in the case of

(a)

(b)

(c)

(d)

In the depletion region of an unbiased P-N junction diode there are

(a) Only electrons	(b) Only holes
(c) Both electrons and holes	(d) Only fixed ions