Question # 1

When we apply reverse bias to a junction diode it

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Lowers the potential barrier

Raises the potential barrier

Increase the majority carrier current

Decrease the majority carrier current

As the electron in Bohr orbit of hydrogen atom passes from stat n = 2 to n = 1 the kinetic energy K and potential energy U change as

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K two-fold,U also two-fold

K four-fold,U also four-fold

K four-fold,U two-fold

At a certain instant a stationary transverse wave is found to have maximum kinetic energy the appearance of string of that instant is:

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Sinusoidal shape with amplitude A/3

Sinusoidal shape with amplitude A/2

Sinusoidal shape with amplitude A

Straight line

A force of 10N is acting along y-axis its component along x-axis is

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10N

20N

100N

Zero N

Energy is stored in the choke coil in the form of

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Heat

Magnetic energy

Electric energy

Electro -magnetic energy

A person standing near the track of a fast moving train has tendency to fall towards it because of

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Vibration due to motion of train

Gravitation force of attraction between person and trains

The high speed of train

Some other effect

Two sources of sound are said to be coherent if

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They produce sounds of equal intensity

They produce sounds of equal frequency

They produce sound waves vibrating with the same phase

They produce sound waves with zero or constant phase difference all instant of time

If a diamagnetic substance is brought near north or south pole of a bar magnet it is

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Attracted by the poles

Repelled by the poles

Repelled by north pole and attracted by the south pole

Attracted by the north pole and repelled by the south pole

A ten-ohm electric heater operates on a 110 V line Calculate the rate at which it develops heat in watts:

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1310 W

670 W

810 W

1210 W

One cannot see through fog because

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Fog absorbs light

The refractive index of fog is infinity

Light suffers total reflection at the droplet in a fog

Light is scattered by the droplets in fog

What is the average energy of N molecules of monoatomic gas?

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1/2 NkT

NkT

3/2 NkT

5/2 NkT

If 2.2 kilowatt power is transmitted through a 10 ohm line at 22000 volt, the power loss in the form of heat will be

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0.1 watt

1 watt

10 watt

100 watt

To explain his theory Bohr used

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Conservation of linear momentum

Conservation of angular momentum

Conservation of quantum frequency

Conservation of energy

If the metal bob is a simple pendulum is replaced by a wooden bob, then its time period will

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Increas

Decreases

Remain the same

First A then B

The temperature at which the speed of sound becomes double as was at 27°C is

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273°C

0°C

927°C

1027°C

The velocity of a particle at an instant is 10 m/s and after 5s the velocity of the particle is 20 m/s. The velocity 3s before in m/s is:

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8

4

6

7

The length of a telescope is 36 cm. The focal lengths of its lenses can be

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30 cm, 6 cm

-30 cm, -6 cm

30 cm, -6cm

-30cm, 6cm

Which of the following is the only vector quantity?

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Temperature

Energy

Power

Momentum

Band spectrum is produced by

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H

He

H₂

Na

Ultra-violet radiation of 6.2 eV falls on an aluminium surface. K.E. of fastest electron emitted is (Work function = 4.2 eV)

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3.2 x 10-21 J

3.2 x 10-19 J

7 x 10-25 J

9 x 10-32 J

The excess (equal in number) of electrons that must be placed on each of two small spheres spaced 3 cm apart, with force of repulsion between the spheres to be 10^-19N, is

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25

225

625

1250

If the amplitude of sound is doubled and the frequency reduced to one-fourth, the intensity of sound at the same point will be

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Increasing by a factor of 2

Decreasing by a factor of 2

Decreasing by a factor of 4

Unchanged

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