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# JEE(MAIN) Physics Mock Test - 3

## 30 Questions MCQ Test JEE Main Mock Test Series 2020 & Previous Year Papers | JEE(MAIN) Physics Mock Test - 3

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This mock test of JEE(MAIN) Physics Mock Test - 3 for JEE helps you for every JEE entrance exam. This contains 30 Multiple Choice Questions for JEE JEE(MAIN) Physics Mock Test - 3 (mcq) to study with solutions a complete question bank. The solved questions answers in this JEE(MAIN) Physics Mock Test - 3 quiz give you a good mix of easy questions and tough questions. JEE students definitely take this JEE(MAIN) Physics Mock Test - 3 exercise for a better result in the exam. You can find other JEE(MAIN) Physics Mock Test - 3 extra questions, long questions & short questions for JEE on EduRev as well by searching above.
QUESTION: 1

Solution:
QUESTION: 2

### The de-Broglie wavelength associated with proton changes by 0.25% if its momentum is changed by P₀. The initial momentum was

Solution: Use the formula lamba=h/p you will see that they are inversely related, so if you reduce wavelength by 0.25% then momentum reduces by 1 unit. So that implies Initial momentum is 401Po
QUESTION: 3

### A fixed volume of iron is drawn into a wire of length l. The extension x produced in this wire by a constant force F is proportional to

Solution:
QUESTION: 4

Condensers of capacities 2 μ F and 3 μ F are connected in series and a condenser of capacity 1 μ F is connected in parallel with them. The resultant capacity is

Solution:
QUESTION: 5

Vapour is injected at a uniform rate in a closed vessel which was initially evacuated. The pressure in the vessel

Solution:

QUESTION: 6

What is the coefficient of mutual inductance, when the magnetic flux changes by 2X10-2 Wb and change in current is 0.01 A ?

Solution:
QUESTION: 7

The electric potential V is given as a function of distance x (metre) by V = (5x2 + 10x - 9) volt. Value of electric field at x = 1m is

Solution:

V = 5x2 + 10x - 9
E = - dv dx
= - (10x + 10)
= -(10 x 1 + 10)
= - 20 V/m

QUESTION: 8

If 3.8 x 10-6 is added to 4.2 x 10-5 giving due regard to significant figures, then the result will be

Solution:
QUESTION: 9

The mass and diameter of a planet have twice the value of the corresponding parameters of earth. Acceleration due to gravity on the surface of the planet is

Solution:
QUESTION: 10

Referring to the above two questions, the acceleration due to gravity is given by

Solution:
QUESTION: 11
Among electron, proton, neutron and $\alpha$ - particle the maximum penetration capacity is for
Solution:
QUESTION: 12
In the following question, a Statement of Assertion (A) is given followed by a corresponding Reason (R) just below it. Read the Statements carefully and mark the correct answer-
Assertion(A): Pendulum of a clock is made of alloys and not of pure metals.
Reason(R): Use of alloys make the pendulum look good.
Solution:
QUESTION: 13
In the following question, a Statement of Assertion (A) is given followed by a corresponding Reason (R) just below it. Read the Statements carefully and mark the correct answer-
Assertion(A): Lifting of aircraft is caused by pressure difference brought by varying speed of air molecules.
Reason(R): As the wings/aerofoils move against the wind, the streamlines crowd more above them than below, causing higher velocity above than below.
Solution:
QUESTION: 14

The ratio of densities of nitrogen and oxygen is 14 : 16. The temperature at which the speed of sound in nitrogen will be same as that of oxygen at 55 oC is

Solution:   p p TN=287K=14∘C
QUESTION: 15
The spectrum of light from an incandescent source is
Solution: The spectrum of colors produced by incandescent lights is continuous, more similar to that which is produced by the sun, and incandescent lights transmit more red wavelengths than fluorescent light.
QUESTION: 16

The wavelength of ultrasonic waves in air is of the order of

Solution:
QUESTION: 17
A bullet hits and gets embedded in a solid block resting on frictionless surface. In this process which one of the following is correct?
Solution:
QUESTION: 18

Two rods of the same length and diameter having thermal conductivities K1 and K2 are joined in parallel. The equivalent thermal conductivity of the combination is

Solution:
QUESTION: 19
A wave front travels
Solution:
QUESTION: 20

The Figure shows a rectangular loop of resistance R, width l and length a being pulled at a constant speed vthrough a region of thickness d(>a)d>a in which a uniform magnetic field of induction BB acting into the plane of paper is set up. The position of the loop at instant t is indicated by x, the distance penetrated by the right edge of the loop into the field with x = 0 at t = 0. (see diagram). Ignore the fringe effects on the magnetic field on the loop.

Q. If a graph is plotted for the flux φB through the loop as a function of the coil position x, which of the following will show the correct graph?

Solution:
QUESTION: 21

The Figure shows a rectangular loop of resistance R, width l and length a being pulled at a constant speed vthrough a region of thickness d(>a)d>a in which a uniform magnetic field of induction BB acting into the plane of paper is set up. The position of the loop at instant t is indicated by x, the distance penetrated by the right edge of the loop into the field with x = 0 at t = 0. (see diagram). Ignore the fringe effects on the magnetic field on the loop.

Q.  If a graph is plotted for the induced e.m.f, e(t) in the loop as a function of x, which of the following will show the correct variation?

Solution:
QUESTION: 22

The Figure shows a rectangular loop of resistance R, width l and length a being pulled at a constant speed vthrough a region of thickness d(>a)d>a in which a uniform magnetic field of induction BB acting into the plane of paper is set up. The position of the loop at instant t is indicated by x, the distance penetrated by the right edge of the loop into the field with x = 0 at t = 0. (see diagram). Ignore the fringe effects on the magnetic field on the loop.

Q. If a graph be drawn for the rate P of joule heating(J>H.) in the loop due to induced current as a function of x, which of the following curves will show the correct variation?

Solution:
QUESTION: 23

The molar mass of hydrogen is 2.02×10-3 kg/mol, and radius of earth is 6.37×106 m, also value of acceleration due to gravity on earth's surface is 9.8 m/s².

Q. The temperature at which the rms speed for molecular hydrogen is equal to the speed of escape from earth is :

Solution:
QUESTION: 24

The molar mass of hydrogen is 2.02×10-3 kg/mol, and radius of earth is 6.37×106 m, also value of acceleration due to gravity on earth's surface is 9.8 m/s².

Q. Radius of moon is 1.74×106 m, and gravitational acceleration on surface of moon is assumed to be 0.16 g, now the temperature at which rms speed for molecular hydrogen is equal to speed of escape from moon is

Solution:
QUESTION: 25

A charged particle of mass m and charge q is in equilibrium under the influence of electric and gravitational fields (of earth) and stays in air, near the surface of the earth. The magnitude of electric field intensity at the location of the charged particle is equal to

Solution: Force due to electric field is qE
force due to gravitation is mg
at equilibrium qE=mg
E=mg/q
QUESTION: 26

A point charge q is placed in space. Consider an arbitrary shaped Gaussian surface which is divided into two parts I and II by an imaginary plane as shown in figure. For this situation mark out the correct statement(s).

Solution:
QUESTION: 27

An ideal gas is found to obey an additional law VP2 = constant during an experiment. The gas is initially at temperature T and volume V. When it expands to a volume 2V, its temperature will become

Solution:
QUESTION: 28

A conducting spherical shell having charge Q is placed near two point charges as shown in figure. Assume all charges to be +ve. For this situation mark out the correct statements(s).

Solution:
QUESTION: 29

A hollow metal sphere of radius 9 cm charged with 5 nC. The electric potential at a point distant 1 cm from the centre is

Solution: V= kq/r
9*10^9 * 5*10^-9/ 9*10^-2

500
QUESTION: 30

Two small particles of equal masses start moving in opposite directions from a point A in a horizontal circular orbit. Their tangential velocities are v and 2v, respectively, as shown in the figure. Between collisions, the particles move with constant speeds. After making how many elastic collisions, other than that at A, these two particles will again reach the point A?

Solution: For first collision relative velocity is 3V
distance covered is 2πr/3v*v =2πr/3 that's one third of circle
now for second collision again relative velocity is 3v
distance covered = 2πr/3v*2v =4πr/3..that's two third of the circle

(I'm mulitpying by 2v in second case since velocities get interchanged )
so finally 2 collision are made