A charge + q is distributed over a thin ring of radius r with line charge density λ = q sin 2 θ ( π r ) . Note that the ring is in the x - y plane and θ is the angle made by r → with the x -axis. The work done by the electric force in displacing a point charge + Q from the center of the ring to infinity is

equal to zero only if the path is a straight line perpendicular to the plane of the ring.

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A heater supplying constant power $P$ watts is switched on at time $t = 0$ minutes to raise the temperature of a liquid kept in a calorimeter of negligible heat capacity. A student records the temperature of the liquid $T (t)$ at equal time intervals. A graph is plotted with $T (t)$ on the $y$ -axis versus $t$ on the $x$ -axis. Assume that there is no heat loss the surroundings during heating. Then,

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Practice Book for KVPY Aptitude Test - Stream SX Physics>Chapter 14 - KVPY PROBLEMS 2019 STREAM - SX>PHYSICS>Q 14

Unpolarised red light is incident on the surface of a lake at incident angle

θ_{R}

. An observer seeing the light reflected from the water surface through a polarizer notices that on rotating the polarizer, the intensity of light drops to zero at a certain orientation. The red light is replaced by unpolarised blue light. The observer sees the same effect with reflected blue light at incident angle

θ_{B}

. Then,

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Practice Book for KVPY Aptitude Test - Stream SX Physics>Chapter 14 - KVPY PROBLEMS 2019 STREAM - SX>PHYSICS>Q 15

A neutral spherical copper particle has a radius of

10 nm (1 nm = 10^{- 9} m)

. It gets charged by applying the voltage slowly adding one electron at a time. Then the graph of the total charge on the particle vs the applied voltage would look like

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Practice Book for KVPY Aptitude Test - Stream SX Physics>Chapter 14 - KVPY PROBLEMS 2019 STREAM - SX>PHYSICS>Q 16

A charge

+ q

is distributed over a thin ring of radius

r

with line charge density

λ = \frac{q \sin^{2} θ}{(π r)}

. Note that the ring is in the

x - y

plane and

θ

is the angle made by

\vec{r}

with the

x

-axis. The work done by the electric force in displacing a point charge

+ Q

from the center of the ring to infinity is

EASY

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Practice Book for KVPY Aptitude Test - Stream SX Physics>Chapter 14 - KVPY PROBLEMS 2019 STREAM - SX>PHYSICS>Q 17

Originally the radioactive beta decay was thought as a decay of a nucleus with the emission of electrons only (case $I$ ). However, in addition to electron, another (nearly) massless and electrically neutral particle is also emitted (case $II$ ). Based on the figure below, which of the following is correct.

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Practice Book for KVPY Aptitude Test - Stream SX Physics>Chapter 14 - KVPY PROBLEMS 2019 STREAM - SX>PHYSICS>Q 18

One gram-mole of an ideal gas

A

with the ratio of constant pressure and constant volume specific heats,

γ_{A} = \frac{5}{3}

is mixed with

n

gram-moles of another ideal gas

B

with

γ_{B} = \frac{7}{5}

. If the

γ

for the mixture is

\frac{19}{13}

what will be the value of

n ?

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Practice Book for KVPY Aptitude Test - Stream SX Physics>Chapter 14 - KVPY PROBLEMS 2019 STREAM - SX>PHYSICS>Q 19

How will the voltage

(V)

between the two plates of a parallel plate capacitor depend on the distance

(d)

between the plates, if the charge on the capacitor remains the same?

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Practice Book for KVPY Aptitude Test - Stream SX Physics>Chapter 14 - KVPY PROBLEMS 2019 STREAM - SX>PHYSICS>Q 20

Three large identical plates are kept close and parallel to each other. The outer two plates are maintained at temperature

T

and

2 T

, respectively. The temperature of the middle plate in steady state will be close to

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Practice Book for KVPY Aptitude Test - Stream SX Physics>Chapter 14 - KVPY PROBLEMS 2019 STREAM - SX>PHYSICS>Q 21

A metal rod of cross-sectional area

10^{- 4} m^{2}

is hanging in a chamber kept at

20 ° C

with a weight attached to its free end. The coefficient of thermal expansion of the rod is

2.5 \times 10^{- 6} K^{- 1}

and its Young's modulus is

4 \times 10^{12}

N m^{- 2}

. When the temperature of the chamber is lowered to

T

then a weight of

5000 N

needs to be attached to the rod so that its length is unchanged. Then

T

Important Questions on KVPY PROBLEMS 2019 STREAM - SX

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