Alternating Current — Physics STD 12 Science — Question

A galvanometer can be used as a voltmeter by connecting a

(a) High resistance in series	(b) Low resistance in series
(c) High resistance in parallel	(d) Low resistance in parallel

A ray of light is incidenting normally on a plane mirror. The angle of reflection will be

(a) 0°	(b) 90°
(c) Will not be reflected	(d) None of the above

An image of the sun is formed by a lens of focal length of 30 cm on the metal surface of a photoelectric cell and a photoelectric current I is produced. The lens forming the image is then replaced by another of the same diameter but of focal length 15 cm. The photoelectric current in this case is

(a)

(b) I

(c) 2I

(d) 4I

The black shapes in the figure are closed surfaces. The electric field lines are in red. For which case the net flux through the surfaces is non-zero?

A river is flowing from west to east at a speed of 5 metres per minute. A man on the south bank of the river, capable of swimming at 10 metres per minute in still water, wants to swim across the river in the shortest time. He should swim in a direction:

1. Due north.
2. 30° east of north.
3. 30° north of west.
4. 60° east of north.

A current carrying power line carries current from west to east. Then the direction of the magnetic field 2m above it is:

In potentiometer a balance point is obtained, when:

The electrical resistance of depletion layer is large because

(a) It has no charge carriers

(b) It has a large number of charge carriers

(c) It contains electrons as charge carriers

(d) It has holes as charge carriers

The permanent magnetic moment of the atoms of a material is not zero. The material:

A set of atoms in an excited state decay.