Online Test

Question # 1

The unit of spring constant

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Nm

Nm^-1

Kgs^-2

Both B and C

SI unit of potential difference is volt it can be written as

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JC^-2

JC^-1

JC

J.A

If Young s double slit experiment is immersed in water then the fringes with

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Decreases

Remains unchanged

Becomes infinite

Increases

Maximum acceleration of an object in simple harmonic motion is 24 m/s² and maximum velocity is 16 m/sec.Then amplitude of SHM is

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32/3 m

3/32 m

2/3 m

3/2 m

The effective component of V_p or the velocity of the particle of given by

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V_p sin (90^o - θ)

V_p cos θ

X_o ω cos θ

All of these

A potential difference 42000 volt is used in an X-rays tube to accelerate electrons. The maximum frequency of the X-radiator produced is

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10¹⁹Hz

10³Hz

10¹⁴Hz

10⁶Hz

A steel wire hangs vertically form a fixed pint, supporting a weight of 80N at its lower end the length of wire form the fixed point to the weight is 1.5 m and mass per unit length is 1.53 x 10^-3kgm^-1. What will be its fundamental frequency

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76 Hz

760 Hz

7 Hz

6 HZ

Doppler affect can be used to calculate the speeds of

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Planets

Distant stars

Galaxies

All of these

The time rate of change of displacement is called

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Speed

Velocity

Acceleration

None of these

When a current-carrying conductor of length 'L' is placed in magnetic field B, this experience a force

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F = IL/B

F = ILB Sinθ

F = BI Sinθ

F = ILB Cosθ

The restoring force applied on the pendulum

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mg cos θ

mg sin θ

- mg sin θ

- mg cos θ

If focal length of objective is increased

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Magnifying power of compound microscope decreased

Magnifying power of astronomical telescope increases

The diameter of the objective lens

None of these

The curie temperature for iron is

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750°C

570°C

750°k

57°K

It is easier to turn a steering wheel with both hands than with a single hand because

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Accelerating force increase on the wheel

Two forces act on the wheel

Two hands provide firm grip

Couple acts on the wheel

Newton's rings are formed due to:

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Diffractin

Interference

Polarization

Manetisation

With the help of LASER which of the following can be measured accurately

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Activity of cancerous

Distance between points

Age of cancerous cells

All of above

Bohr's third postulate about the transition of an electron from higher to lower energy state, is

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hf = E_p - E_n

hf_o = E_p - E_n

hf = E_n - E_p

None of these

The coil of the moving coil galvanometer comes to rest after the application of

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Deflecting torque

Restoring torque

When deflecting and restoring torque are eqal

None of these

As circular coil has 250 turns and a mean diameter of 20 cm. If carries a current of 5A. What is the strength of the magnetic field at a point on its axis at a distance of 5m from the centre of the coil ?

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4π × 10^-7 T

2π × 10^-7 T

2π × 10^-8 T

Every point of a wavefront may be considered as a

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Source

Source of wavefront

Source of secondary wavefront

None of these

In projectile motion, the acceleration in horizontal is

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Maximum

Minimum

Zero

None of these

The direction of the angular velocity vector is along

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The tangent to the circular path

The inward radius

The outward radius

The axis of rotation

A new type of optical fibre in which central core has high refractive index and its density gradually decreases towards its periphery is called

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Step index fibre

Multimode step index fibre

Multimode graded index

None of these

The reactance of coil depends upon the

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Frequency of D.C. and inductance L

Frequency of A.C. and inductance L

Frequency of D.C. and current I

None of these

Linear momentum is a vector quantity and has direction of

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Its displacement

Velocity

Acceleration

None of these

If you are to choose a light from the given below,which one may be the most suitable for photoelectric effect?

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Visible light

Ultra-violet light

Infra-red light

Far-infra light

In an X-ray tube, the intensity of the emitted X-ray beam is increased by

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Increasing the filament current

Decreasing the filament current

Increasing the target potential

Decreasing the target potential

Which of the following gives three regions of the electromagnetic spectrum in order of increasing wavelength?

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Gamma rays,microwaves,visible radiation

Ultraviolet infra-red microwaves

Radio waves ultraviolet X-rays

Visible radiation gamma rays radio waves

In the Compton's effect, it is found that the wavelength of incident X-rays is

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greater than the wavelength of scattered X-rays

equal to the wavelength of scattered X-rays

less than the wavelength of scattered X-rays

any one of them

Thermodynamic temperature scale works

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For very high temperature only

For moderate temperature only

Even up to absolute Zero

None of these

The dimensions of ½at²are of

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length

Velocity

Acceleration

TIme

Is Boyle's law is applicable, to the isothermal process

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No

Yes

Some what applicable

None of these

The needle of the dip circle at a place stays at 30°.The dip circle is inclined at an angle of 30° with the magnetic meridian. The true dup at the place is:

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tan^-1 √3

tan ^-1 √3/5

tan ^-1 √1/2

tan^-1 4/2

The orbital speed for the circular orbit must be equal to the average speed of the satellite for

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one year

one month

one day

one hour

Relative biological effectiveness (RBE) of α-particles from natural radioactivity is

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2 RBE

5 RBE

10 RBE

11 RBE

The decrease in potential energy of a ball of mass 20 kg which falls from a height 50 cm is:

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968 J

98 J

1980 J

None of these

Acceleration means the speed of the body is

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Increasing

Decreasing

Just stop

None of these

What will be the colour of the sky as seen from the earth if there were no atmosphere ?

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Black

Blue

Orange

Red

Find the gain of operational amplifier when R₁= Infinity R₂= 0

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15

100

77

1

The ratio of number of protons and the number than the electrons is:

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Almost one in lighter elements

Greater than one in heavy elements

Smaller than one in heavy elements

Both A and C

Both A and B

For CE npn transistor the current gain β is

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I_c/ I_b

1_c / I_e

I_e / I_b

I_b / I_c