Magnetism And Matter — Physics STD 12 Science — Question

Assertion :  Electron has higher mobility than hole in a semiconductor.

Reason     : Mass of electron is less than the mass of hole.

(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.

A short sighted person can see distinctly only those objects which lie between 10 cm and 100 cm from him. The power of the spectacle lens required to see a distant object is

(a) + 0.5 D

(b) – 1.0 D

(c)  – 10 D

(d)  + 4.0 D

A reaction between a proton and  that produces  must also liberate

(a)

(b)

(c)

(d)

A vertical straight conductor carries a current vertically upwards. A point P lies to the east of it at a small distance and another point Q lies to the west at the same distance. The magnetic field at P is

(a) Greater than at Q

(b) Same as at Q

(c) Less than at Q

(d) Greater or less than at Q depending upon the strength of the current

In a charge free region, electric field lines can be taken to be continuous curves:

For a particle executing simple harmonic motion, the acceleration is proportional to:

1. Displacement from the mean position.
2. Distance from the mean position.
3. Distance travelled since t = 0.
4. Speed.

Energy gaps between the highest band and the lowest empty bands in elements A, B, C and D are 0,70,530 and 90 kJmol−1. Then,

An A.C. circuit containing only capacitance, the current:

An arc of a circle of radius R subtends an angle   at the centre. It carries a current i. The magnetic field at the centre will be

(a)

(b)

(c)

(d)

One metallic sphere A is given positive charge whereas another identical metallic sphere B of exactly same mass as of  A is given equal amount of negative charge. Then

(a) Mass of  A and mass of  B still remain equal

(b) Mass of  A increases

(c) Mass of  B decreases

(d) Mass of  B increases