10EPT20F

A piece of copper and another of germanium are cooled from room temperature to 80 K. The resistance of ....

• Each of them increases

• Each of them decreases

• Copper increases and that of germanium decreases

• Copper decreases and that of germanium increases

All the bulbs above are identical. which bulb(s) light(s) most brightly ?(2) 2 only(3) 3 and 4

• (1) 1 only

• (2) 2 only

• (3) 3 and 4

• (4) 1 and 5

If other factors remain constant, which of the following combinations of number of turns per 20 cm and electric current respectively in a solenoid produce the weakest electromagnet ?

• 500 turns & 3 A

• 700 turns & 2 A

• 200 turns & 5 A

• 300 turns & 4 A

A wire is placed vertically between the poles of a horse-shoe magnet, such that the north pole is to your left and south pole is to your right. It carries a direct current flowing upwards then it will experience a force tending to deflect it

• to your left

• to your right

• away from you

• towards you

The ratio of equivalent resistance across A and B when switch is open to that when switch is closed is ...

• 3/8

• 5/8

• 7/8

• 9/8

A charged particle moves through a region of magnetic field pointing in the direction perpendicular to its direction of velocity. Then during its subsequent motion

• Its momentum changes but the kinetic energy remains constant.

• Its momentum and kinetic energy both changes.

• Its momentum and kinetic energy both remains constant.

• Its kinetic energy changes but the momentum remains constant.

A body starts performing uniform circular motion such that it covers 100 rounds per min. Then the minimum time after which its average velocity will be zero is

• 0.5 s

• 0.6 s

• 0.7 s

• 0.8 s

For a body of 50 kg mass, the velocity-time graph is shown in figure. Then force acting on the body is ,,,,

• 25 N

• 50 N

• 12.5 N

• 100 N

Superconductors are materials that appear to exhibit no resistance. Therefore, electrons passing through a superconductor will

• generate no current

• generate no heat

• increase the current’s power

• decrease the electrons’ charge

A conductor with rectangular cross-section has dimensions (a × 2a × 4a) as shown in figure. Resistance across AB is x, across CD is y and across EF is z. Then ...

• x = y = z

• x > y > z

• y > z > x

• x > z > y