Question # 1

If the distance between the plates of a parallel plates capacitor is increased, its potential will:

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Remain the same

Increase

Decrease

Decrease exponentially

Light elements do not emit X-rays because

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Electrons in it have high binding energy

These materials are non- material

There is a small difference in their energy shells

Electrons in it require very large energy to remove from these materials

Two artificial satellites of unequal masses are revolving in a circular orbit around the earth with a constant speed. Their time periods:

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Will be different

Will depend on their masses

Will be same

Will depend upon the place of their projection

What will be efficiency of carnot engine when it is operated between the temperatures 47^oC and 127 ^oC:

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Reversible

Irreversible

Sometimes A and B

None of these

Rest mass energy of electron is:

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1.02 MeV

0.51 MeV

931 MeV

200 MeV

The temperature at which all the gases become liquid is called:

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273 K

-273 K

Absolute Zero

Both (B) and (C)

Ten second after an electric fan is turned on, the fan rotates at 300rev/min. its average angular acceleration is

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30 rad/s²

3.14 rad/s²

30 rev/s²

500 rev/s²

If temperature of the sink is decreased, efficiency of a carnot engine.

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Remains constant

Decreases

Increases

None of these

A photo cell is based on:

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Compton effect

Pair production

Photo cell

All of these

In an ideal gas, the molecules have:

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Kinetic energy only

Potential energy only

Both KE and PE

None of these

If a transverse wave has a speed of 10 m/ sec and frequency of 10 cycle/ sec itswavelength is:

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1 m

10^-2 cm

10 m

10 cm

Maximum speed of electrons in X-rays tube which is producing X-rays photons of frequency f is

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The Balmer series is found in the spectrum of:

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Hydrogen

Nitrogen

Oxygen

All

Light of frequency 4f0 is incident on the metal of the threshold frequency f0. The maximum kinetic energy of the emitted photoelectrons is

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3h f0

3/2h f0

2h f0

1/2h f0

The method by which only one half of A.C cycle is converted into direct current is called

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half wave amplification

half wave rectification

Full wave rectification

full wave amplification

A radioactive substance has a half-life of 4 months. Three-fourths of the substance will decay in:

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5months

6months

8months

7months

Ratio of dimension of K.E and power is:

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1:1

T:1

1:T

M:J

A piece of Aluminium (Al) and a piece of Germanium (Ge) are cooled T1 K to T2 K. The resistance of:

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Each of them increases

Each of them decreases

Al increases and Ge decreases

Al decreases and that of Ge increases

If a car moves with a uniform speed of 2 ms-1 in a circle of radius 0.4m. Its angular speed is

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4 rad. s^-1

1.6 rad. s^-1

5 rad. s^-1

2.8 ms^-1

de-Broglie wavelength associated with an electron moving at a speed of 1x106 ms-1 is

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4x10-10 ms-1

5x10-10 m

6x10-10 m

7x10-10 m

The nature of thermal radiation is smaller to:

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Ultraviolet rays

Light rays

Both of them

None of these

The de-Broglie wavelength of the particle of mass m and energy E is:

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ℎ

𝜆 = ℎ√2𝑚𝐸

𝜆 = 1

An electron is moving towards high potential. Its electrical P.E:

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Increases

Remains constant

Decrease

May increase may decrease

The diode charactristics curve is plot between

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I & t

V& t

V& I

None

In thermodynamics, the change in internal energy depends upon:

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The path taken between initial and final states

The initial state only

The final state only

Initial and final states

A person holds a bucket of weight 60N. He walks 7 m along the horizontal path and then climbs up a vertical distance of 5 m. The work done by the man is:

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300 N-m

420 N-m

720 N-m

none of these

Electromagnetic waves emitted by hot bodies are called:

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Photoelectrons

Alpha rats

Thermal radiation

None of these

An electron and a proton are projected at right angles to a uniform magnetic field with

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the electron trajectory will be less curved than proton’s trajectory

the electron trajectory will be more curved than proton’s trajectory

) both trajectories will be equally curved

) both particles continue to move along a straight lins

If P is the pressure and V is the volume, Then PV will represent:

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Power

Work

Force

None of these

The shortest wavelength of X-rays emitted from an X-rays tube depends on the:

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Current in the tube

Voltage applied to the tube

Nature of gas in the tube

Nature of material of tube

A man pushes a wall and fails to displace it. He does:

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Negative work

Positive but not maximum work

No work at all

Maximum work

Torque is necessary for producing.

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angular speed

linear acceleration

angular acceleration

none of these

The stopping potential for a certain metal is 10 volt, the max. Energy of emitted electron is:

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10 J

100 J

1.6 × 10-18 J

1.6 × 10-19 J

Which of the following work is greater?

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+ 100J

0 J

- 100J

Both A and B are equal

Charge on a capacitor is 50C. if voltage applied across its plates is 10V then its capacitance:

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5F

0.02F

500F

0.2F

Which combination of 7 identical resistors of 3-ohm will give 12/13 ohm:

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3 series, 4 parallel

5 series, 2 parallel

2 series, 5 parallel

4 series, 3 parallel

Two charges of equal magnitudes and at a distance r exert a force F on each other. If the charges are halved and distance between them is doubled, then the new force acting on each charge is:

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F/8

F/4

F/16

4F

electrons from the surface of a metal when:

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It is heated to a high temperature

Radiation of suitable wavelength falls on it

Electrons of suitable velocity strike it

It is placed in a strong electric field

The efficiency of full wave rectifier is:

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25.6%

81.2%

81.6%

71.2%

For X-rays which of the following is not correct:

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Cause of ionization in air when they pass through it

Can be deflected by electric and magnetic fields

Can be used to detect flaws in metal casting

Travel with the speed of light