WBJEE Physics Test - 14


40 Questions MCQ Test WBJEE Sample Papers, Section Wise & Full Mock Tests | WBJEE Physics Test - 14


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Attempt WBJEE Physics Test - 14 | 40 questions in 60 minutes | Mock test for JEE preparation | Free important questions MCQ to study WBJEE Sample Papers, Section Wise & Full Mock Tests for JEE Exam | Download free PDF with solutions
QUESTION: 1

The work function of metals A and B are in the ratio 1 : 2. If light of frequencies f and 2f are incident on metal surfaces of A and B respectively, the ratio of the maximum kinetic energies of photo electrons emitted is (f is greater than threshold frequency of A, 2f is greater than thershold frequency of B)

Solution:
QUESTION: 2

Two uniform wires A and B are of the same metal and have equal masses. The radius of wire A is twice that of wire B. The total resistance of A and B when connected in parallel is

Solution:
QUESTION: 3

If there is an increase in length by 0.1% due to stretching, the percentage increase in its resistance willbe

Solution:
QUESTION: 4

The work done in stretching a wire by 1mm is 2J. The work necessary for stretching another wire of same material but with double the radius of cross-section and half the length by 1mm is in Joules

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QUESTION: 5

There are two bodies of masses 100 kg and 10,000 kg separated by a distance 1 cm. At what distance from the smaller body, the intensity of gravitational field will be zero

Solution:
QUESTION: 6

An electric dipole of dipole moment p is placed in uniform electric field of strength E. If θ is the angle between p and E, then potential energy of the dipole becomes maximum, when θ is

Solution:
QUESTION: 7

Eddy currents are produced when

Solution:

Eddy currents are produced when a metal is kept in a varying magnetic field.

QUESTION: 8

An electric dipole consists of two opposite charges of magnitude  q seperated by 2a. When the dipole is placed in uniform electric field E, to have minimum potential energy, then dipole moment p makes which the following angle with E

Solution:
QUESTION: 9

If the force on a rocket moving with a velocity of 300 m−s-1 is 210 N, then the rate of fuel combustion is

Solution:
QUESTION: 10

A cell is connected between two points of a uniformly thick circular conductor. i₁ and i₂ are the currents flowing in two parts of the circular conductor of radius a. The magnetic field at the centre of the loop will be

Solution:
QUESTION: 11

If an ammeter is to be used in place of voltmeter, then we must connect with the ammeter a

Solution:
QUESTION: 12

Force between two identical bar magnets whose centres are r metre apart is 4.8 N when their axes are in the same line. If the separation is increased to 2 r meters, the force between them is reduced to

Solution:
QUESTION: 13

The shape of a liquid drop becomes spherical due to its

Solution:
QUESTION: 14

A body projected vertically upwards with a velocity u returns to the starting point in 4 s. If g=10 m−s-2, the value of u is

Solution:
QUESTION: 15

A boat is sent across a river with a velocity of 8 km h-1. If the resultant velocity of boat is 10 km h-1, then the velocity of river is

Solution:
QUESTION: 16

An aeroplane moving horizontally with a speed of 720 km-h-1 drops a food packet, while flying at a height of 405 m. The time taken by the food packet to reach the ground and its horizontal range is (Take g = 10 m−s-1)

Solution:
QUESTION: 17

The first atomic reactor was constructed by

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QUESTION: 18

An instantaneous displacement of a simple harmonic oscillator is x = A cos (ωt + π/4 ). Its speed will be maximum at time

Solution:

The velocity is the time derivative of displacement: v = dy/dt = -Aω (sinωt + π/4).
Its maximum magnitude equal to Aω is obtained when ωt = π/4 , from which t = π/4ω

QUESTION: 19

A prism is made up of material of refractive index 3 . The angle of the prism is A. If the angle of minimum deviation is equal to the angle of the prism, then the value of A is

Solution:

We know for a prism
μ = sin A + D 2 sin A/2
3 = sin 2A 2 sin A/2 = 2 cos A/2
⇒ cos A 2 = 3 2
A/2 = 30
A = 60o

QUESTION: 20

A particle has simple harmonic motion. The equation of its motion is x =5 sin (4t-π/6), where x is its displacement. If the displacement of the particle is 3 units, then its velocity is

Solution:
QUESTION: 21

The moment of inertia of a straight thin rod of mass M and length l about an axis perpendicular to its length and passing through its one end, is

Solution:
QUESTION: 22

A solid cylinder of mass M and radius R rolls down an inclined plane without slipping. The speed of its centre of mass when it reaches the bottom is

Solution:
QUESTION: 23

In case of a semiconductor which of the following statement is wrong

Solution:
QUESTION: 24

Wires P and Q have the same resistance at ordinary(room) temperature. When heated resistance of P increases and that of Q decreases. We conclude that

Solution:
QUESTION: 25

19g of water at 30 oC and 5g of ice at − 20 oC are mixed together in a calorimeter. What is the final temperature of the mixture ? Given specific heat of ice = 0.5 cal g-1  oC-1 and latent heat of fusion of ice = 0.8 cal g-1

Solution:
QUESTION: 26

Measurement of current will be more accurate, when it is measured by

Solution:
QUESTION: 27

A mass of liquid with volume V₁ is completely changed into a gas of volume V₂ at a constant external pressure P and temprature T. If the latent heat of evaporation for the given mass is L, then the increase in the internal energy of the system is

Solution:
QUESTION: 28

If are vectors forming a reciprocal system to the vectors  then is equal to

Solution:
QUESTION: 29

In Young's double slit interference experiment the wavelength of light used is 6000 Å . If the path difference between waves reaching a point P on the screen is 1.5 microns, then at that point P

Solution:
QUESTION: 30

Two equal masses m₁ and m₂ moving along the same straight line with velocities + 3m/s and -5 m/s respectively collide elastically. Their velocities after the collision will be respectively

Solution:
QUESTION: 31

A charge Q is distributed over two concentric metal shells of radii r and R(> r) such that the surface charge densities on the outer surfaces of the two shells are equal. The charge density of the inner sphere is

Solution:
QUESTION: 32

In the circuit below, A and B represent two inputs and C represents the output. The circuit represents

Solution:
QUESTION: 33

A thin uniform rod of length l and mass m is swinging freely about a horizontal axis passing through its end. Its maximum angular speed is ω . Its centre of mass rises to a maximum height of-

Solution:
QUESTION: 34

A mixture of light, consisting of wavelength 590 nm and an unknown wavelength, illuminates Young's double slit and gives rise to two overlapping interference patterns on the screen. The central maximum of both lights coincide. Further, it is observed that the third bright fringe of known light coincides with 4th bright fringe of the unknown light. From this data, the wavelength of the unknown light is-

Solution:
QUESTION: 35

The velocity of a particle is v = v0 + gt + ft2. If its position is x = 0 at t = 0, then its displacement after unit time (t = 1) is

Solution:
QUESTION: 36

A rectangular loop carrying a current i is situated near a long straight wire such that the wire is parallel to one of the sides of the loop and is in the plane of the loop. If steady current I is established in the wire as shown in the figure, the loop will

Solution:
QUESTION: 37

For a given plate voltage, the plate current in a triode value is maximum when the potential of

Solution:
QUESTION: 38

Two identical charged particles enter a uniform magnetic field with same speed but at angles 300 and 600 with the field. Let a,b and c be the ratios of their time periods, radii and pitches of the helical paths. Then

Solution:
QUESTION: 39

Which of the following statements are false?

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QUESTION: 40

A wave equation which gives the displacement along the y-direction is given by y = 10-4sin(60t + 2x) where x and y are in metre and t is time in second. This represents a wave

Solution:
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