Question # 1

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

Initially, four identical uniform blocks, each of mass m and thickness h, are spread on a table How much work is done on the blocks in stacking them on top of one another?

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2 mgh

3 mgh

4mgh

6mgh

When heat is added to the system, the entropy change is:

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Positive

Negative

Zero

None of these

A whistle is revolved with high speed in a horizontal circle of radius R. to an observer at the centre of the circle the frequency of the whistle will appear to be:

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Decreasing

Increasing

Both

Constant

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

The efficiency of a practical heat engine:

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Can be 100%

Can not be 100%

Is always Zero

None of these

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

The distance between the plates of a charged parallel plate capacitor is 4mm and potential difference is 6 volts. If the distance between the plates is increased to 12mm, then :

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The potential difference of the capacitor will become 18 volts

The P.D become 20 volts

The P.D will remain unchanged

The charge on condenser will reduce to one third

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

In a closed organ pipe, the fundamental frequency is f. What will be the ratio of thefrequencies of the next three overtones?

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2 : 3 : 4

3 : 7 : 11

3 : 4 : 5

3 : 5 : 7

A steady current is flowing in a conductor of non-uniform cross-section. Thecharge passing through any cross-section per unit time is

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Directly proportional to the area of cross-section

Inversely proportional to the area of cross-section

Proportional to square of the area of cross-section

Independent of the area of cross-section

The fusion of hydrogen into helium is more likely to take place:

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At high temperature and high pressure

At high temperature and low pressure

At low temperature and low pressure

At low temperature and high pressure

The only significant motion possessed by the mono-atomic gas molecules is:

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Translatory

Rotatory

Vibratory

None of these

The potential difference applied to an X-rays tube is increased. As a result, in the emitted radiation

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The intensity increases

The minimum wavelength decrease

The intensity remains unchanged

Both B & C

A device which convert DC into AC is calleD)

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Invertor

Generator

Rectifier

Motor

The mother and daughter elements with the emission of 𝖰 − 𝒓𝒂𝒚𝒔, are called:

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Isotopes

Isobars

Isomers

Isodiapheres

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

Which one is the case when the wavelength is actually changed?

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When source move relative to observer

When observer move relative to source

When observer moves around a stationary source at the center of circle

When the relative displacement between source and observer is zero

When resistances are connected in Parallel, the effective resistance will be

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Product of the reciprocals of the individual resistances

Product of the individual resistances

Sum of the reciprocals of the individual resistances

Sum of the individual resistances

A magnetic field

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Always exerts a force on a charged particle

Never exerts a force on a charged particle

Exerts a force on a charged particle if it is moving across the magnetic lines of force

Exerts a force on a charged particle if it is moving along the magnetic lines of force.

The momentum of a particle is numerically equal to its K.E. What is the velocity of a particle?

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9 ms^-1

3 ms^-1

2 ms-1

1 ms^-1

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

A sonar depth finder in a boat uses sound signals to determine the depth of water. Fourseconds after the sound leaves the boat it returns to the boat because of reflection fromthe bottom. Assume the speed of sound in water is 1,460 meters per second. The depth of the water is, in meters, :

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2,200

4,800

4,400

2,920

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

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reflection

refraction

diffraction

transmission

The time period of a geostationary satellite above the surface of the earth is.

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24 hours

12 hours

365 days

none of these

In electron microscope, we use high speed electrons because them

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Penetration power is higher

Wavelength is smaller

Frequency is smaller

K.E is smaller

During a negative β-decayv

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An atomic electron is ejected

A neutron in the nucleus decays emitting an electron

An electron which already present within the nucleus is ejected

A part of binding energy of nuclei is converted into electron

The centre of gravity of a triangular plate is at

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On end of the plate

The midpoint of any side of the plate

Two bodies are projected at angle 𝜽 𝒂𝒏𝒅 (𝟗𝟎 − 𝜽) to the horizontal with the same speed. The ratio of their times of flight is:

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sin 𝜃 : 1

cos 𝜃 : 1

sin 𝜃 : cos𝜃

cos 𝜃 : sin𝜃

A proton, accelerated through a p.d V has a certain de Broglie wavelength. In order to have the same de Broglie wavelength, an 𝑎 −particles must be accelerated through a potential difference:

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4V

8V

V/4

V/8

A rider uses Motorcycle safety helmet that extends the time of collision during accident hence decreasing the

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Change of collisio

Force acting

Velocity

Impulse

In case of planets the necessary acceleration is provided by

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Gravitational force

coulomb force

frictional force

centripetal force

Absolute zero is considered as that temperature at which:

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All liquids become gases

All gases become liquids

Water freezes

None of these

Davisson and Germer received the Nobel prize for their work on:

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Wave nature of particle

Corpuscular nature of wave

Dual nature of particle

All of them

Interference and diffraction of light confirms its:

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Particle nature

Dual nature

Wave nature

Electromagnetic nature

A closed organ pipe and an open organ pipe have their first overtone identical infrequency. Their lengths are in ratio

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3:4

1:2

2:3

3:5

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)

The time period of revolution of geostationary satellite is

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1440 minutes

24 minutes

84 minutes

none of these

Only those processes are probable to take place for which entropy os the system:

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Increases

Remains constant

Both A and B are correct

None of above

The minimum energy required to remove an electron is called:

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Stopping potential

Work function

Kinetic energy

None of these

The binding energy per nucleon is:

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Greater for heavy nuclei

Least for heavy nuclei

Greatest for light nuclei

Greatest for medium nuclei