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WBJEE Physics Test - 9

40 Questions MCQ Test WBJEE Sample Papers, Section Wise & Full Mock Tests | WBJEE Physics Test - 9

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Attempt WBJEE Physics Test - 9 | 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

In photo electric effect the stopping potential is

A.
Increases with increase of frequency of incident light
B.
Decreases with increase of frequency of incident light
C.
First increases and then becomes constant with increase of frequency of incident light
D.
Is independent of frequency of incident light

Solution:

In the photoelectric effect is that the stopping potential is a function of the frequency of the incident light. As shown in Figure, there is even a cutoff frequency ν₀ below which there is no photoelectric effect occurs, regardless of the intensity of the light.

A plot of stopping potential vs. frequency of incident light (Cathode: Sodium ; Cutoff frequency νo =4.39x 10¹⁴ Hz
Hence option (A) is correct.

QUESTION: 2

A strip of copper and another of germanium are cooled from room temperature to 80 K. The resistance of

A.
Each of these increases
B.
Each of these decreases
C.
Copper strip increases and that of germanium decreases
D.
Copper strip decreases and that of germanium increases

Solution:

QUESTION: 3

Under elastic limit the stress is

A.
Inversely, Proportional to strain
B.
Directly, proportional to starin
C.
Square root of strain
D.
Independent of strain

Solution:

QUESTION: 4

The resistance of a conductor increases with

A.
Increase in length
B.
Increase in temperature
C.
Decrease in cross-sectional area
D.
All of these

Solution:

QUESTION: 5

The current flowing in a step down transformer 220 V to 22 V having impedance 220 Ω is

A.
1 A
B.
0.1 A
C.
1 mA
D.
0.1 mA

Solution:

QUESTION: 6

If electric flux entering and leaving an enclosed surface is φ₁ and φ₂ respectively, the electric charge inside the enclosed surface will be

A.
(φ₁+φ₂)ε₀
B.
(φ₂-φ₁)ε₀
C.
(φ₁+φ₂)/ε₀
D.
(φ₂-φ₁)/ε₀

Solution:

QUESTION: 7

A charge q is placed at the centre of a cube. The magnitude of electric flux through one of its face will be

A.
q/ε₀
B.
q/3ε₀
C.
q/6ε₀
D.
6q/ε₀

Solution:

QUESTION: 8

If both the mass and radius of the earth decreases by 1%

A.
The escape velocity would increase
B.
The accleration due to gravity would increase
C.
The escape velocity would decrease
D.
The acceleration due to gravity would decrease

Solution:

QUESTION: 9

A machine gun fires a bullet of mass 40 g with a velocity 1200 m−s⁻¹. The man holding it can exert a maximum force of 144 N on the gun. How many bullets can he fire per second at the most?

A.
one
B.
two
C.
three
D.
four

Solution:

QUESTION: 10

Proton and α -particle projected perpendicularly in a magnetic field, if both move in a circular path with same speed. Then ratio of their radii is

A.
1 : 2
B.
2 : 1
C.
1 : 4
D.
1 : 1

Solution:

QUESTION: 11

A charged particle moves in a circular path in a uniform magnetic field. The radius of circular path is R. When kinetic energy of particle is doubled, then new radius will be

A.
√2R
B.
2R
C.
R/2
D.
R/√2

Solution:

QUESTION: 12

Which of the following materials is repelled by an external magnetic field?

A.
Iron
B.
Cobalt
C.
Steel
D.
Copper

Solution:

QUESTION: 13

A liquid flows through a pipe of non-uniform cross-section. If A₁ and A₂ are the cross-sectional areas of the pipe at two points, the ratio of velocities of the liquid at these points will be

A.
A₁ A₂
B.
A₁/A₂
C.
A₂/A₁
D.
1/A₁A₂

Solution:

QUESTION: 14

A body moves from rest with a constant acceleration of 5 m/s². Its instantaneous speed (in m/s) at the end of 10 sec is

A.
50
B.
5
C.
2
D.
0.5

Solution:

QUESTION: 15

Two bodies are projected with the same velocity. If one is projected at an angle of 30º and the other at an angle of 60º to the horizontal, the ratio of the maximum heights reached is

A.
3 : 1
B.
1 : 3
C.
1 : 2
D.
2 : 1

Solution:

QUESTION: 16

When decays to become the particle released is

A.
Electron
B.
α - particle
C.
Neutron
D.
Positron

Solution:

QUESTION: 17

When the displacement is half of the amplitude, then what fraction of the total energy of a simple harmonic oscillator is kinetic ?

A.
2/7th
B.
3/4th
C.
2/9th
D.
5/7th

Solution:

QUESTION: 18

A particle is projected with certain velocity at two different angles of projections with respect to horizontal plane so as to have same range 'R' on a horizontal plane. If 't₁' and 't₂' are the time taken for the two paths, then which one of the following relations is correct?

A.
t₁t₂ = 2R/g
B.
t₁t₂ = R/g
C.
t₁t₂ = R/2g
D.
t₁t₂ = 4R/g

Solution:

QUESTION: 19

A spring is stretched by 10 cm when a mass of 1 kg is hanged from it. Now, with the same mass if the spring is pulled and then released, then its time period is 9g=10 m/s²)

A.
π/5
B.
2π/5
C.
π/10
D.
π

Solution:

QUESTION: 20

In a laboratory four convex lenses L₁, L₂ ,L₃ and L₄ of focal lengths 2, 4, 6 and 8cm, respectively are available. Two of these lenses form a telescope of length 10cm and magnifying power 4. The objective and eye lenses are respectively

A.
L₂, L₃
B.
L₁, L₄
C.
L₁, L₂
D.
L₄, L₁

Solution:

QUESTION: 21

A particle performing uniform circular motion has angular momentum L. If its angular frequency is doubled, and its K.E. halved, then the new angular momentum is

A.
L/4
B.
2/L
C.
4 L
D.
L/2

Solution:

QUESTION: 22

The radius of a rotating disc is suddenly reduced to half without any change in its mass. Then its angular velocity will be

A.
Four times
B.
Double
C.
Half
D.
Unchanged

Solution:

QUESTION: 23

The process of adding impurities to the pure semiconductor is called

A.
Drouping
B.
Drooping
C.
Doping
D.
None of these

Solution:

QUESTION: 24

The dominant contribution to current comes from holes in case of

A.
metals
B.
intrinsic semiconductor
C.
p-type extrinsic semiconductor
D.
n-type extrinsic semiconductor

Solution:

QUESTION: 25

540 g of ice at 0ºC is mixed with 540 g of water at 80ºC. The final temp. of the mixture in ºC will be

A.
40ºC
B.
79.9ºC
C.
0ºC
D.
80ºC

Solution:

QUESTION: 26

We can not define coefficient of linear or real expansion for a gas, because

A.
it has definite shape
B.
it has an indefinite shape
C.
K.E. of gas molecules is very fast
D.
K.E. of gas molecules is very slow

Solution:

QUESTION: 27

The dimensions of stress are equal to

A.
Force
B.
Pressure
C.
Work
D.
1/Pressure

Solution:

QUESTION: 28

If are any three mutually perpendicular vectors of equal magnitude a then is equal to

A.
a
B.
√2 a
C.
√3 a
D.
none of these

Solution:

QUESTION: 29

In young's double slit experiment, three light, blue, yellow and red are used successively. For which colour, will the fringe width be maximum?

A.
Blue
B.
Yellow
C.
Red
D.
All of the above

Solution:

QUESTION: 30

A body of mass 3 kg is under a force which causes a displacement in it given by S = t²/3. Find the work done by the force in first 2 seconds

A.
2 J
B.
3.8 J
C.
5.2 J
D.
2.6 J

Solution:

QUESTION: 31

The speed of sound in oxygen (O₂) at a certain temperature is 460 ms⁻¹. The speed of sound in helium (He) in the same temperature will be (assumed both gases to be ideal)

A.
460 ms⁻¹
B.
500 ms⁻¹
C.
650 ms⁻¹
D.
None of these

Solution:

QUESTION: 32

A stone tied to the end of a sting of 1 m long is whirled in a horizontal circle with a constant speed. If the stone makes 22 revolutions in 44 seconds, what is the magnitude and direction of acceleration of the stone?

A.
and along the radius towards the centre.
B.
and along the radius away from the centre.
C.
and along the tangent to the circle.
D.
and along the radius towards the centre.

Solution:

QUESTION: 33

Reading shown on two spring balances S₁ and S₂ are 120 kg and 30 kg. respectively, and the lift is accelerating upwards with acceleration 10 m/s². The mass is stationary with respect to lift. Then the mass of the block will be

A.
60 kg
B.
45 kg
C.
90 kg
D.
None of the above

Solution:

QUESTION: 34

The pressure-volume graph of an ideal gas cycle consisting of isothermal and adiabatic processes is shown in the figure. The adiabatic process is described by

A.
AB and BC
B.
AB and CD
C.
BC and CD
D.
AD and BC

Solution:

QUESTION: 35

In the given diagram ,the input is across the terminals A and C and the output is across B and D .Then the output is

A.
zero
B.
same as the input
C.
full-wave rectified
D.
half-wave rectified

Solution:

*Multiple options can be correct

QUESTION: 36

A parallel plate capacitor is charged and the charging battery is then disconnected. If the plates of the capacitor are moved farther apart by means of insulating handles

A.
the charge on the capacitor increases
B.
the voltage across the plates increases
C.
the capacitance increases
D.
the electrostatic energy stored in the capacitor increases

Solution:

*Multiple options can be correct

QUESTION: 37

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

A.
travelling with a velocity of 30 m/s in the negative x-direction
B.
of wavelength π m
C.
of frequency (30/π) hertz
D.
of amplitude 10^-4 m travelling along the negative x-direction

Solution:

*Multiple options can be correct

QUESTION: 38

A diverging lens and an object are positioned as shown in the Figure. Which of the rays A, B, C and D could emanate from point Q at the top of the object?

A.
A
B.
B
C.
C
D.
D

Solution:

*Multiple options can be correct

QUESTION: 39

A binary star has stars of masses m and nm (where n is a numerical factor) having separation of their centres as d. If these stars revolve because of gravitational force of each other, then

A.
the period of revolution is given by
B.
the period of revolution is given by
C.
reduced mass is
D.
reduced mass is

Solution:

QUESTION: 40

For the cyclic process shown in the P-V diagram, the area of the bigger triangle is 4A while that of the smaller triangle is A. Which of the following is/are true?