Question # 1

In a full wave rectifier, the diode conducts during

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Both halves of the input cycle

A portion of the positive half cycle of the input

Positive half cycle of the input

Both halves of the input cycle

The half-life of a certain element is 3.5 days at STP. If the temperature is doubled and pressure is reduced to half then half-life of the same element will be:

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1.75 days

3.5 days

7 days

14 days

A closed organ pipe and an open organ pipe have their first overtones of identicalfrequency. Their respective lengths are in the ratio:

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1 : 2

4 : 3

2 : 3

3 : 5

A man has weight 980 N in a stationary lift. What will be his weight if the lift starts moving up with anacceleration of 4.9 ms^-2

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980 N

1470 N

1980 N

1460 N

The law, governing the force between electric charges is known as:

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Ampere’s law

Ohm’s law

Coulomb’s law

Faraday’s law65y7uhnb

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

A machine gun fires ‘n’ bullets per second and the mass of each bullet is m. If v is the speed of each bullet then the force exerted on the machine gun is:

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mng

mnv

mnvg

mnv/g

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

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

Which of the following is a unit of energy?

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unit

whatt

Horse Power

None of the above

The frequency and work function of an incident photon are n and𝝋𝟎. If f0 is the threshold frequency, then necessary condition for the emission of photo electron is:

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< 𝑓0

𝑓 ≥ 𝑓0

f = 𝑓0/2

None of these

The magnetic field of a solenoid is quite similar to that of a:

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Straight conductor

A horse shoe magne

Any magnet

A bar magnet

In full wave rectification by bridge the number of diodes required are

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3

4

2

5

Hotness and coldness of an object is represented in terms of:

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Heat

Temperature

Chemicial

None of these

The hydrogen atoms are excited to the stationary state designated by the principal quantum number n=4, the number of maximum spectral lines are observe:

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2

3

4

6

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

The relative permittivity of air is

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1

3.7

7.8

1.0006

A process in which no heat enters or leaves the system is called.

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Adiabatic process

Isothermal process

Isochoric process

None of these

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

Carnot cycle is:

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Reversible

Irreversible

Sometimes A, Sometimes B

None of these

The magnetic field due to the electric current in a conducting wire is:

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Towards the centre of the conducting wire

Circular around the conducting wire

In the direction of the electric current

In the direction opposite to the electric current

One degree of thermodynamics scale of temperature is called:

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Celsius

Fahrenheit

Kelvin

Radian

If source and observer are moving towards each other with same speed and aftercrossing they are receding each other then frequency observed by observer:

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Decreases

Remains constant

Increases

First Increases then decreases

The unit of gain (G) for non-inverting amplifier is

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Ampere

ohm

Volt

None of these

If an electron vertically downwards, then the horizontal component of the earth’s magnetic field will deflect it to wards

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West

East

North

A particular wavelength received from a galaxy is measured on earth and isfound to be 5% more than that its wave length on earth. Hence galaxy is

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Moving towards earth

Going away from earth

Stationary with respect to earth

None

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

Pressure may be defined as_____per second per unit area:

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Change in force

Change in momentum

Change in energy

Work done

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

In which of the following, Doppler’s effect is not applicable?

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To find speed of satellite

To find objects under water

To find speed of star

To tune a musical instrument

When ultraviolet rays are incident in metal plate, then photoelectric effect does not occur. It occurs by the incidence of:

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x-rays

Infrared rays

Radio wave

Greenhouse effect

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

Speedometer of an automobile measures

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Average velocity

Instantaneous velocity

Acceleration

Instantaneous speed

Rest mass energy of electron is:

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1.02 MeV

0.51 MeV

931 MeV

200 MeV

A point on the rim of wheel 400 cm in diameter has a velocity of 1600 cms-1 . The angular velocity of the wheel is:

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6 rad/s

4 rad/s

2 rad/s

8 rad/s

The pressure exerted on the walls on the vessel by gas molecules is defined as:

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Force per unit volume

Energy per unit area

mass per unit volume

None of these

In photo electric cell, the photo electric current

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Decreases with increase in frequency of light

Depends on intensity and frequency of light

Does not depend upon the frequency of light and but depends upon intensity of light

Increases with increase in frequency of light

Two 8 N forces act on each end of the beam of length 0.60m. Two forces are parallel and acting opposite to each other, the angle between the force and beam is 60o , what is the torque of the couple exerted on the beam:

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2.4 Nm

4.2 Nm

4.8 Nm

9.6 Nm

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

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

Which one of the following particles projected perpendicular to a uniform magnetic field with the same velocity will be deflected least?

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Electron

Proton

Deuton

None of these