Question # 1

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

If the K.E. of a body is increased by 300%, its momentum will increase by:

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100 %

150 %

√300%

175 %

The energy which an -e acquires when accelerated through a potential difference of 1 volt is called?

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1 Joule

1 Electron volt

1 Erg

1 Watt

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

The maximum wavelength of a transverse wave that can be set up in a string of length Lis

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L

2L

V

4L

Speedometer of an automobile measures

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Average velocity

Instantaneous velocity

Acceleration

Instantaneous speed

Which of the following statement is true about soft X-rays?

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They have large wavelength

They have high energy

They have low energy

Both A and C

The body at rest may have:

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Energy

Momentum

Speed

Velocity

The kinetic energy of a body rotating with an angular speed 𝑚 depends on.

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angular speed

distribution of mass

neither (A) nor (B)

both (A) and (B)

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 simplest type of rectification known as half wave rectification is obtained by

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Using a transistor

Suppressing the harmonics in A.C. voltage

Suppressing half wave of A.C. supply by using diode

Using a Coolidge

Carnot cycle is:

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Reversible

Irreversible

Sometimes A, Sometimes B

None of these

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

3 joules of work is done in 3 seconds, then power is:

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6 watt

3 watt

18 watt

1 watt

In Compton effect, it was considered that X-rays consist of:

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Electrons

Positrons

Photons

All of these

A 100W, 220V bulb is operated on a 110V line, the power consumed is:

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25W

75W

50W

100W

The temperature scale approved in SI units is:

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Calslus scale

Kelvin scale

Fehrenhelt scale

None of these

The frequency of the fundamental mode of open at one organ pipe is 400 Hz. Ifone end of pipe is closed the fundamental frequency will be

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800 Hz

600 Hz

400 Hz

200 Hz

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

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reflection

refraction

diffraction

transmission

How many photons per second does a one-watt bulb emit if its efficiency is 10% and the wavelength of light is 500 nm:

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2.53 × 1017

2.53 × 1019

7.5 × 1019

7.5 × 1017

The most penetrating radiations out of the following is that of

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𝛾-rays

β-rays

α-particles

X-rays

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

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

A gas which strictly obeys the gas laws under all conditions of temperatures and pressure is called:

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Ideal gas

Inert gas

Real gas

None of these

Thermal radiations are a type of:

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Mechanical waves

Electromagnetic waves

Alpha rays

Electrons

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

The dimensions of Planck’s constant “h” are same as that of:

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Momentum

Angular momentum

Work

Torque

. Time rate of change of momentum is equal to

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Force

Impulse

Velocity

Both A and C

In order to perform experiment, Davisson and Germer used accelerating voltage of:

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54V

120V

220V

400V

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 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

A boy is travelling from Lahore to Karachi with uniform velocity . Its

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Speed changes

Acceleration changes

Direction of motion changes

Displacement from origin changes

The shortest wavelength of X-rays emitted from an X-rays tube depends on the:

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Current in the tube

Voltage applied to the tube

Nature of gas in the tube

Nature of material of tube

A stone of mass 0.5kg tied with a string of length 1m is moving in a horizontal circle with a speed of 4ms-1 . The tension acting on the string in newton is:

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2

0.2

8

0.8

A body of mass m tied to a string is moved in a vertical circle of radius r. the difference in tensions at the lowest point and the highest point is.

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2 mg

4 mg

6 𝑚g

8 mg

A particle is moving with constant speed by keeping itself at constant distance from a fixed point in a given plane. Its motion is

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Circular motion

Uniform circular motion

Uniform circular motion with fixed axis of rotation

Uniform circular motion with axis of rotation not defined

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

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Translatory

Rotatory

Vibratory

None of these

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

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

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Isotopes

Isobars

Isomers

Isodiapheres

A long solenoid has 20 turns/ cm. The current necessary to produce a magnetic field of 20 mellites inside the solenoid is approximately:

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1A

2A

4A

8A

When the length and area of cross-section both are doubled, then its resistance:

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Will become half

Will remain the same

Will be doubled

Will become four times