Question # 1

The equation W = ________𝜟U represents:

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Thermal process

adiabatic process

Isobaric process

None of these

A charge of 2C experiences a force 2000N in a uniform electric field. In this fieldthe potential difference between two points separated by a distance 1cm is

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2V

10V

5V

20V

The maximum energy of the photoelectrons can be determined by making the:

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Anode positive

Anode negative

Cathode positive

Both (b) & (c)

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

A soap bubble is give a negative charge, then its radius:

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Decrease

Remains same

Increases

Bubble will disappear

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

The angular analogue of linear displacement is called

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angular velocity

angular displacement

angular momentum

moment of force

Photo cells are used for :

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Security and counting system

Automatic door system

Automatic street lighting

All of these

The activity of a radioactive sample is 1.6 curie and half-life is 2.5 days. Its activity after 10 days will be:

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0.8 Curie

0.1Curie

0.4 Curie

0.16 Curie

A stone attached to one end of a string is revolved around a stick so that the string winds on the stick and gets shortened) What is conserved)

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angular momentum

kinetic energy

linear momentum

none of the above

The efficiency of half wave rectifier is:

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25.6%

1.2%

40.6%

66.6%

The energy stored in wound watch spring is

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K.E.

P.E.

heat energy

chemical energy

A man M₁ of mass 80 kg runs up a staircase in 15s. Another man M₂ also of mass 80 kg runs up the same staircase in 20s. The ratio of the power developed by them will be

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1

4/3

16/9

none of these

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

The energy of photon of wavelength 620 nm is:

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0.5 eV

1.0 eV

1.5 eV

2.0 eV

Figure represents a graph of kinetic energy (K) of the photoelectrons (in eV) and frequency (v) for a metal used as cathode in photoelectric experiment. The work function of metal is:

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1 eV

2 eV

1.5 eV

3 eV

When the length and area of cross-section both are doubled, then its resistance:

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Will become half

Will remain the same

Will be doubled

Will become four times

A source of a magnetic field is:

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An isolated magnetic

A static electric charge

A moving electric charge

None of these

The law of thermodynamics which discusses the condition under which heat energy is converted into and equivalent amount of work is:

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1st

2nd

3rd

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 a molecule with momentum mv strikes a wall and rebound then the change in momentum will be:

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-2 mv

Zero

2 mv

mv

Rest mass energy of electron is:

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1.02 MeV

0.51 MeV

931 MeV

200 MeV

Light of frequency 1.5 times the threshold frequency is incident on a photo sensitive material. If the frequency is halved and intensity is doubled the photo electric current becomes

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Four times

Half

Double

Zero

The maximum wavelength of a transverse wave that can be set up in a string of length Lis

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L

2L

V

4L

A stationary wave is established in a string which vibrates in four segments at afrequency of 120 Hz. Its fundamental frequency is:

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15Hz

60Hz

30Hz

430Hz

Two satellites are going around the earth at a height of 250 km and 450 km respectively. If angular speed for both is same, then centripetal acceleration will be.

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more for first

more for second

same for both

nothing can be decided

The rate of change of momentum of a body falling freely under gravity is equal to its

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Impulse

Kinetic energy

Pover

Weight

The time period of revolution of geostationary satellite is

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1440 minutes

24 minutes

84 minutes

none of these

The work done to keep the satellite in the given orbit is.

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Zero

infinity

unit

can’t be decided

The phenomenon of radioactivity is associated with:

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Fission of nucleus

Disintegration of neutrons

Emission of spectral lines

Spontaneous disintegration of the nuclei of atoms

If a body changes its momentum from 100 N s to 200 N s in 10 s then the unbalanceexternal force responsible to change the momentum is

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5 N

2.5 N

2n

10n

Which one is the correct express of de-Broglie equation for the length of atoms of mass m at temp? T(k=Boltzmann’s constant):

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For a particle in circular motion the centripetal acceleration

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may be more or less than its tangential acceleration

equal to its tangential acceleration a

more than its tangential acceleration

less than its tangential acceleration

The frequency of the fundamental mode of open at one organ pipe is 400 Hz. Ifone end of pipe is closed the fundamental frequency will be

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800 Hz

600 Hz

400 Hz

200 Hz

The body at rest may have:

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Energy

Momentum

Speed

Velocity

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

The coulomb’s law is valid for the charges which are:

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Moving and point charges

Stationary and point charges

Moving and non-point charges

Stationary and large size charges

. A force "F1" acts on a body through distance "S1" in the direction of motion and does work "W1". Similarly another force "F2" act on same body through distance "S2" but in opposite to the direction of motion and does work "W2". Now if F1 = F2 and S1 = S2 then which statement is correct.

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W1 = W2

W2< W2

W1 > W2

W1 = W2= 0

A bomb of mass 30 kg at rest explodes into two pieces of masses 18 kg and 12 kg. The velocity of 18 kg mass is 6 ms¹ The KE of other mass is

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324 J

256 J

245 J

524 J

If a rotating body is moving counter clockwise, direction of angular velocity will be

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along linear velocity

towards the center

along the axis of rotation

away from center

A thorium nucleus is formed when a uranium nucleus emits an 𝑎 −particles. Atomic number of thorium is :

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23

60

90

70