Question # 1

Two point charges +2 coulombs and +6 coulombs repel each other with a force of 12 N if a charge -4 coulomb is given to each of these charges the force will be:

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4N repulsive

8N repulsive

4N attractive

8N attractive

Light of frequency 2 times the threshold frequency is incident on the metalsurface. Ifthe frequency is by quartered and intensity is doubled, the photoelectric becomes

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Quadrupled

Zero

Doubled

Halved

A positively charged particle is moving perpendicular to a uniform magnetic field. The magnetic force makes the particle to move along:

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An elliptical path

A circular path

A parabolic path

None of these

In photoelectric effect, if we increase the frequency of the incident light then of the electrons increased

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Number

K.E

P.E

Frequency

An elevator's motor produces 3000 W power. The speed With Which it can lift a 1000 kg load is:

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30.6ms^-1

0.306ms^-1

3.06ms^-1

300.3ms^-1

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

At constant temperature, if the density of the gas is increased, its pressure will:

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Decrease

Increase

Remain unchanged

None of these

When passes from medium to another, deviate from its path is called

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reflection

refraction

diffraction

transmission

The magnetic field produced due to the current in a straight wire is proportionalto the :

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Electric current

Conducting material

Length of the wire

Diameter of the wire

A non-inverting amplifier has infinite input resistance then the voltage gain of noninverting amplifier will be:

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Zero

Infinite

One

100

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

What will be the number of photons emitted per second by 25 W source of monochromatic light of wavelength 600 nm:

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7.5 × 1017

7.5 × 1019

5.5 × 1019

5.5 × 1017

If the momentum of a body is increased n times, its kinetic energy increases:

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n times

2 n times

√𝑛 times

n 2 time

For a body moving with constant speed in a horizontal circle, which of the following remains constant?

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Velocity

Centripetal force

Acceleration

Kinetic energy

An electric motor exerts a force of 40 N on a cable and pulls it by a distance of 30 m in one minute. The power supplied by the motor in watts is

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20

200

2

10

The body at rest may have:

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Energy

Momentum

Speed

Velocity

Change in momentum per second is:

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Product force and time

Product of pressure and area

Ratio of pressure and area

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

The angular momentum changes form 2 units to 6 units in 4s. the torque is

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1 unit

3/2unit

1/2unit

4unit

An engine pumps out 40 kg of water in one second. The water comes out vertically upwards with a velocity of 3ms-1 . What is the power of engine in kilowatt?

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1.2kW

120kW

12kW

1200kW

Two bodies moving towards each other collide and move away in opposite directions. There is some rise in temperature of bodies because a part of the kinetic energy is converted into

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heat energy

electrical energy

nuclear energy

mechanical energy

A monkey is accelerating down a string whose breaking strength is two third of his weight. The minimumacceleration of the monkey should be

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1/3g

g

2/3 g

0 m/s2

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

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

Threshold wavelength for metal having work function 𝝋 is 𝝀. What is the threshold wavelength for metal having work function 2 𝒊𝒔:

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/𝟐

2

4

𝝀/𝟒

G.P Thomson revealed:

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Particle nature of electron

Dual nature of electron

Wave nature of electron

Electromagnetic nature of electron

In a photocell, sodium and potassium emit electrons for:

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Visible light

Infrared light

Ultraviolet light

All of these

As the working substance of a heat engine completes a cycle, there is no change in:

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Internal energy

Pressure

Volume

All of these

A church organ consist of open ended pipes ranging from 4m to 4 mm, if the speed ofsound is considered as 400 m/s then the min and max frequency is:

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400 Hz and 4 kHz

100 Hz and 100 kHz

50 Hz and 50kHz

400 Hz and 400 kHz

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

A person weighing 20 mg walks on a level platform with a speed of 2 ms-1 . The work by the person against the force of gravity is:

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Zero

2J

60J

600J

Carnot cycle is:

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Reversible

Irreversible

Sometimes A, Sometimes B

None of these

The mud flies off the tyre of a fast moving car in the direction

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parallel to the moving tyre

anti parallel to the moving tyre

tangent to the moving tyre

none of these

Intensity of light from a point source at the edge of unit sphere will be:

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𝑃

P(4π)

4𝜋

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

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

Two astronauts in a satellite must have

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Same masses

Same real weights

Same apparent weights

None of these

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

A count rate 240 per minute reduces to 30 counts per min in 1 hour. The half-life of source is:

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20min

60min

80min

90min

The energy of photon of energy 1 eV is:

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1240 nm

1040 nm

1000 nm

620 nm

The relative permittivity of air is

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1

3.7

7.8

1.0006