Question # 1

The method by which only one half of A.C cycle is converted into direct current is called

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half wave amplification

half wave rectification

Full wave rectification

full wave amplification

Rest mass energy of electron is:

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1.02 MeV

0.51 MeV

931 MeV

200 MeV

A force of 6 N act horizontally on a stationary mass of 2kg for 4s. The kineticenergy in joule is

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12

72

56

888

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

Resistance of 60 watt bulbs in 120V line is:

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20 ohms

240 ohms

0.15 ohms

180 ohms

An organ pipe open at both ends and another organ pipe, closed at one end willresonate with each other, if their lengths are in ration of

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1:1

1:4

2:1

1:2

In a one-dimensional elastic collision, the relative velocity of approach before collision is equal to:

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Sum of the velocities of the bodies

e times the relative velocity of separation after collision

1⁄𝑒 times the relative velocity of separation after collision

relative velocity of separation after collision

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

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𝑃

P(4π)

4𝜋

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

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 listener observes the frequency “f” of stationary source. If it move toward with 3 times of velocity of sound. Then the apparent frequency of the sound will be

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f

3f

f/2

4f

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

A body of mass m kg is lifted by a man to a height of one meter in 30 sec. Another man lifts the same mass to the same height in 60 sec. The work done by them are in the ratio

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1: 2

1: 1

2: 1

4: 1

With the propagation of longitudinal waves through a material medium, the quantitiestransferred in the direction of propagation are:

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Energy, momentum and mass

Energy and momentum

Energy and mass

Energy

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

When a particle moves in a circle the angle between it linear velocity and the angular velocity is always

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0°

180°

90°

none of them

Diffraction pattern has also been observed for:

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Proton

Neutron

Hydrogen atom

All of them

The product of resistance and conductance of a resistors is equal to:

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1

Conductivity

Resistivity

Zero

Carnot engine is ____________ heat engine.

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A reversible

An irreversible

An ideal

Both A and C

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 same retarding force is applied to stop a train. The train stops after 80 m. If the speed is doubled, then the Stopping distance will be:

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The same

Doubled

Halved

Four times

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

A stone is thrown up from the surface of earth when it reaches at maximum height. its total energy is equal to

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mgh

1/2 𝑚𝑣²

zero

2mgh

Maximum speed of electrons in X-rays tube which is producing X-rays photons of frequency f is

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A sonometer wire 100 cm in length has a fundamental frequency of 330 Hz. Thevelocity of propagation of waves along the wire is

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115m/sec

660m/sec

990m/sec

Vertical component of velocity of the projectile at any instant ‘t’ from the ground is given by:

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𝑣𝑖𝑐𝑜𝑠𝜃

𝑣𝑖𝑐𝑜𝑠𝜃 − 𝑔t

𝑣𝑖𝑠𝑖𝑛𝜃 − 𝑔t

𝑣𝑖𝑠𝑖𝑛𝜃 + 𝑔t

The emf of a cell of negligible internal resistance is 2V. It is connected to the series combination of 𝟐𝛀, 𝟑𝛀 𝐚𝐧𝐝 𝟓𝛀 resistance. The potential difference across 𝟑𝛀 resistance will be in volt:

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0.6

2/3

3

6

A photo cell is based on:

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Compton effect

Pair production

Photo cell

All of these

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

A light and a heavy body have equal momenta. Which one has greater K.E?

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The light body

The heavy body

The K.E are equa

Data is incomplete

SI unit of kinetic energy of rotation is

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joule second

joule

joule second

joule meter

A body of mass 3 Kg lies on the surface on the table 2m high. It is moved on the surface by 4m. The change of P.E will be:

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Zero

9.8 J

19.6 J

329 J

An electron is moving towards high potential. Its electrical P.E:

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Increases

Remains constant

Decrease

May increase may decrease

The rate of change of momentum of a molecule is equal to:

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Pressure

Work

Density

Force

Because of large mass when 𝑎 −paricle enters the atom or molecule it:

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Moves in zigzag path

Moves along straight line

Moves along circular path

None of these

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

At constant temperature, if the volume of a given mass of a gas is doubled, then the density of gas becomes:

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Double

Remains constant

Half

None of these

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

When a person lifts a body from ground work done by lifting force is?

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Positive

Negative

Zero

Half of positive maximum

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

Photo cells are used for :

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Security and counting system

Automatic door system

Automatic street lighting

All of these