Online Test

Question # 1

Colour of thin film will not show result from

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Scattering of light

Dispersion of light

Interference of light

Both a and b

Application of photoelectric effect is

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Photo diode

Photo transistor

Photocell

None of these

The pressure of a given mass of gas, at constant temperature, is inversely proportional to its volume.

The above statement states which gas law?

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Boyle's law

Dalton's law

Charles Law

Newton's Law

When an observer is standing on a railway platform, the pitch of the whistle of an approaching train is heard to be

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higher

lower

unchanged

all of them

If two non zero vectors A and B obey the relation |A + B| = |A - B|.then the angle between them is:

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120°

90°

60°

0°

Fundamental forces of nature are

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weak nuclear force

strong nuclear force

electromagnetic force and weak nuclear force

all of them

According to the law of conversion of linear momentum, the total linear momentum of an isolated system

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increases

decreases with time

remains constant

none of them

Resistor is a device which converts electrical energy to

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heat energy

chemical energy

elastic energy

all of them

1 year = ______.

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3.1536 x 10⁷s

3.1536 x 10^-7s

3.1536 x 10¹⁰s

3.1536 x 10^-10s

An object is placed between the focus and the optical center of the convex lens. The image formed is

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Real, erect and magnified

Virtual, inverted and magnified

Virtual, erect and diminished

Virtual, erect and magnified

Classical physics is still valid in

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Very small particles

Fast moving particles

Ordinary process

None of these

The colour of platinum wire changes to yellow at

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1000 ^oC

1200 ^oC

1300 ^oC

1800 ^oC

Suppose the water flows out from a pipe at 3 kgs^-1and its velocity changes from 5 ms^-1 to zero on striking the ball, then force is

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5.3 N

15 N

17.3 N

19.2 N

The best conductor is:

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Silver

Copper

Aluminium

Both (B) and (C)

None of them

In an ac circuit with voltage V and current 1 the power dissipated is

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VI

1/2 VI

1/√2 VI

Depends on the phase between V and I

In depletion region

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Holes are not present

Electrons are not present

Both are not present

None of these

The viscosity of water is

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0.019 x 10^-3 Nsm^-2

0.801 x 10^-3 N-sm^-2

6.29 x 10^-3 N-sm^-2

0.081 x 10³ N-sm^-2

A.C has replaced D.C in our homes because

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A.C is more safe

A.C can be transmitted economically

production cost of D.C is more

A.C can be produced easily

What is the maximum possible efficiency of a steam engine that uses steam at a temperature of 100°C on a day when the temperature is 300K? (round off the answer to the nearest whole number?

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19%

20%

80%

81%

In a never system, the repeaters are placed at about

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50 km

75 km

100 km

125 km

The decay constant of a radioactive element is 1.5 x 10^-9 per second.Its mean life in seconds will be

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1.5 x 10⁹

4.62 x 10⁸

6.67 x 10⁸

10.35 x 10⁸

The practical unit of current is:

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Ampere

Ohm

Coulomb

Volt

None of these

Conductors are those materials in which energy gap is

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very large (several eV)

very narrow (= 1eV)

either of them

none of them

A heat engine converts thermal energy to mechanical work which is

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All

Partly

Some

None of these

A conducting rod is moved through a uniform magnetic field The emf induced across its ends does not depend upon

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Magnetic flux density

Length of the rod

Orientation of rod

Thickness of the rod

Applied voltage across the X plates of CRO is provided by

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Provided by circuit that is built in CRO

Sweep generator

Time base generator

All are true

A body of mass 5 kg is moving in a circle of radius 1 m with an angular velocity of 2 rad/s.The centripetal force is

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10 N

20 N

30 N

40 N

A simple pendulum consists of a

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Small heavy bob

Big metallic bob

Big light bob

None of these

When a silicon crystal is doped with a trivalent element, such an extrinsic semi-conductor is called

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p-type semi-conductor

n-type semi-conductor

either of them

none of them

The energy of the 4th orbit in hydrogen atom is

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2.5 eV

- 3.5 eV

- 0.85 eV

- 13.6 eV

The principle of rocket motion is based on the

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First law of motion

Second law of motion

Third law of motion

None of these

Which component of weight balance the tension T in the string

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mg cos θ

mg sin θ

- mg cos θ

None of these

Low penetration power

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α-particle

β-particle

γ-particle

None of these

The SI unit of conductivity is

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ohm m

ohm^-1m^-1

ohm m^-1

ohm^-1m

Sound in air exhibits all the order properties of waves except

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Deflection

Diffration

Refraction

Polarization

The collection time of electrons and holes of solid state detector is much less than gas filled counters, therefore it counter

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Fast

Low

Very low

None of these

Which of the following forces have long range

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Strong nuclear force

Electromagnetic force

Weak nuclear force

All are true

The value of 'γ' for monatomic gas is

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1.40

1.67

1.17

1.29

The angle between A and B is θ.The value of the triple product A,(B x A) is:

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A²B

Zero

A²B sin θ

A²B Cos θ

A steel bar can bear a load of 20 tons. If the thickness of bar is double, then for the same depression it can bear a load of:

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40 ton

80 ton

160 ton

5 ton

A very high energy photon interact with matter and changes into

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Electron

Positron

Pair of electron and positron

None of these