Question # 1

The maximum energy of the electrons released in a photo cell is independent of:

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Frequency of incident light

Intensity of incident light

Nature of cathode rays

None of these

A diode characteristics curve is a graph plotted between;

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Current and time

Voltage and time

Voltage and current

Forward voltage and reverse current

A force 𝑭 = (𝟓𝒊̂+ 𝟑𝖩̂) newton is applied over a particle which displaces it from its origin to the point 𝒓 = (𝟐𝒊̂− 𝟏𝖩̂) meters. The work done on the particle is:

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– 7 joules

+13 joules

+ 7 joules

+11 joules

The maximum kinetic energy of emitted photoelectrons depends upon:

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The intensity of incident light

Frequency of the incident light

Temperature of the surface

All of above

A body is in translational equilibrium if

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P = 0

L = 0

F = 0

 = 0

The power output of a full wave rectifier is:

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Equal to H.W.R

Twice of H.W.R

Half of H.W.R

Four times of H.W.R

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

For a normal AC cycle, during T/2 to T the diode act as:

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Open switch

full wave rectifier

Close switch

All are correct

Compton Effect makes the use of the law of conservation of:

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Energy

Momentum

Charge

Both (a) & (b)

A pure semiconductor has:

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An infinite resistance at 0^oC)

A finite resistance which does not depend upon temperature

A finite resistance which decreases with temperature

A finite resistance which increase with temperature

A body crosses the topmost point of a vertical circle with critical speed. Itscentripetal acceleration, when the string is horizontal will be

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4g

3g

g

6g

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

The energy stored in wound watch spring is

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K.E.

P.E.

heat energy

chemical energy

The momentum of the moving photon is:

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Zero

ℎ

𝜆

ℎ𝜆

The gravity does no work, when the body moves:

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Horizontally

Vertically upwards

Vertically downward

At an angle of 45o with horizontal

When the velocity of a body is doubled:

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Its K.E is doubled

Its P.E is doubled

Its momentum is doubled

Its acceleration is doubled

If the stone is thrown up vertically and return to ground, its potential energy is maximum

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during the upward journey

at the maximum height

at the bottom

When two objects come to common temperature, the body is said to be in:

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Static equilibrium

Dynamic equilibrium

Thermal equilibrium

None of these

Moving photons posses:

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Energy

Momentum

Wavelength

All of these

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

A PN junction diode cannot be use:

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As rectifier

For converting light energy to electrical energy

For getting light radiation

For increasing the amplitude of an ac signal

The specific resistance of a wire varies with its:

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Length

Cross-section

Mass

Material

A parallel plate air capacitor is charged and then isolated. When a dielectric material is inserted between the plates of the capacitor , then which of the following does not change:

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Electric field between the plates

Charge on the plates

Potential difference across the plate

Energy stored in the capacitor

In full wave rectification, the output D.C. voltage across the load is obtainedfor

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The positive half cycle of input A.C. (C) The complete cycle of input A.C.

The negative half cycle of input A.C.

The complete cycle of

All of the above

Diffraction pattern has also been observed for:

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Proton

Neutron

Hydrogen atom

All of them

A cell of negligible resistance and e.m.f 2 V is connected across a series combination of 2,3 and 5 ohms. The p.d. across the 3 Ω resistor is

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0.6 V

1/3 V

2/3 V

4/3 V

Choose incorrect about properties of photon

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Rest mass of photon is zero

A photon is never at rest

Photon is not deflected by electric field not by magnetic field

The velocity of photon is different in different media

A radioactive isotope 𝟐𝟑𝟖 𝑼 decays consecutively to 𝟐𝟑𝟒 𝑼 the particles emitted are:

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One 𝛼 and one 𝛽

Two 𝛼 and one 𝛽

e 𝛼 and two 𝛽

Two 𝛼 and two 𝛽

De-Broglie received the Nobel prize in

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1929

1937

1928

1924

The example of nuclear fusion is:

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Formation of barium and krypton from uranium

Formation of plutonium -235 from uranium -235

Formation of helium from hydrogen

Formation of water from hydrogen and oxygen

Temperature of black body radiating at 270c is increased to 327oc, then emittedenergywill increase by

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2 times

12 times

16 times

4 times

A motor boat is travelling with a speed of 3.0 m/sec. If the force on it due to water flow is 500 N, the power of the boat is

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150 KW

1.5 KW

heat energy

chemical energy

Two wires of same material have lengths L and 2L and cross-sectional area 4A and A respectively. the ratio of their specific resistance would be:

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1: 1

1: 8

8: 1

1: 2

Most motorbikes have ____________ cylinder/s engine but cars usually have _________ cylinders on the same crankshaft.

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Four , Six

One , four

two , five

None of these

A body revolved around the sun 27 times faster then the earth what is the ratioof their radii

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1/27

1/4

1/9

1/3

The fundamental frequency in a stretched string is 10 Hz. To double the frequency, the tension in it must be changed to:

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T₂ = 2T₁

T₂ = 4T₁

T₂ = T₁

none of these

Charge to mass ratio (e/m) of a charge particle is also called its:

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Specific charge

Specific Force

Gyro-magnetic ratio

Magneto-mechanical ratio

The wavelength of light observed on the earth, form a moving star is found todecrease by 0.05%. Relative to the earth the star is

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moving away with a velocity of 1.5 x 10⁵m/s

moving away with a velocity of 1.5 x 10⁴m/s

coming closer with a velocity of 1.5 x 10⁵m/s

coming closer with a velocity of 1.5 x 10⁴m/s

In full wave rectification, the output DC voltage across the load is obtained for.

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The positive half cycle of input AC only

The negative half cycle of input AC

The completes cycle of input AC only

All of the above

A body gets positive charge. It means that:

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It has lost electrons

It has gained positions

It has gained protons

It has gained 𝛼 −particles

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

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ℎ

𝜆 = ℎ√2𝑚𝐸

𝜆 = 1