# Test: Physics - 3

## 20 Questions MCQ Test Science & Technology for UPSC CSE | Test: Physics - 3

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Attempt Test: Physics - 3 | 20 questions in 20 minutes | Mock test for UPSC preparation | Free important questions MCQ to study Science & Technology for UPSC CSE for UPSC Exam | Download free PDF with solutions
QUESTION: 1

### Consider the following statements and select the correct code. Assertion (A): In our houses, the current in A.C. electricity line changes direction 60 times per second. Reason (R): The frequency of alternating voltage supplied is 50 Hz.

Solution:

In our houses, the frequency of alternating voltage supplied is 50 Hz, i.e. 50 times per second. In America, frequency of A.C. line is 60 Hz.

QUESTION: 2

### Consider the following statements: 1. If magenta and yellow-coloured circles intersect, the intersected area will have red colour." 2. If cyan and magenta coloured circles intersect, the intersected area will have blue colour. Q. Which of the statement(s) given above is/are correct?

Solution:

The intersected area of magenta and yellowcoloured circles will have red colour. The intersected area of cyan and magenta coloured circles will have blue colour. Magenta = Red + Blue Cyan = Blue + Green

QUESTION: 3

### Consider the following statements: 1. A flute of smaller length produces waves of lower frequency. 2. Sound travels in rocks in the form of longitudinal elastic waves only. Q. Which of the statement(s) given above is/are correct?

Solution:

Sound travels in rocks in the form of longitudinal elastic waves only.

QUESTION: 4

Which of these pairs has the same unit of measurement?

Solution:

Pressure and Coefficient of Elasticity have the same unit i.e. Nm-2 (Newton per metre square) Other important units: Rate of Flow: m3s-1 Acceleration: ms-2 Rydberg constant: 1/m Gas constant: J/K Impulse: Ns Moment of Force: Nm

QUESTION: 5

Match List-I with List-II and select the correct answer using the codes given below:

Solution:

Joule denoted by coulomb–volt. Watt denoted by amp2–ohm. Volt denoted by henery–amp/sec. Coulomb denoted by farad–volt.

QUESTION: 6

Which of the following statements are true regarding heat?
1. Heat is a form of energy.
2. Heat can be reflected by mirror.
3. Heat is an electromagnetic radiation.
4. Heat can pass through a vacuum.
Q. Select the correct answer from the codes given:

Solution:

Heat is a form of energy. Heat can be reflected by mirror. Heat can pass through a vacuumHeat is transferred by thermal radiation. Heat cannot conduct through a vacuum because that requires molecules to move to carry the thermal energy.

QUESTION: 7

Ultrasonic waves are used for stirring liquid solutions because they

Solution:

Ultrasonic waves can produce perfectly homogeneous solution. It is used in homogenising milk cosmetics, etc.

QUESTION: 8

According to the modern theory of nature of light, the light has

Solution:

According to the modern theory of nature of light, the light has both wave and particle nature.

QUESTION: 9

According to Coulomb’s law, the electrostatic force between two charges is

Solution:

The electrostatic force between two charges is inversely proportional to the square of the distance between the charges.

QUESTION: 10

What is the difference between a CFL and an LED lamp?
1. To produce light, a CFL uses mercury vapour and phosphorus while an LED lamp uses semiconductor material.
2. The average lifespan of a CFL is much longer than that of LED lamp.
3. A CFL is less energy - efficient as compared to an LED lamp.

Q. Which of the statement(s) given above is/are correct?

Solution:

To produce light, a CFL uses mercury vapour and phosphorus while an LED lamp uses semiconductor material.

QUESTION: 11

Heavy water is used as a moderator in a nuclear reactor. The function of the moderator is

Solution:

The function of the moderator is to slow down the neutrons.

QUESTION: 12

What does the term Dolby B or Dolby C printed on tape recorders and other sound systems refer to?

Solution:

The term Dolby B or Dolby C printed on tape recorders and other sound systems refers to noise reduction circuit.

QUESTION: 13

A man inside an artificial satellite feels weightlessness because the force of attraction due to earth is

Solution:

A man inside an artificial satellite feels weightlesness because the force of attraction due to earth i.e. g (= acceleration due to gravity) is zero.

QUESTION: 14

A liquid drop tends to assume a spherical shape because of

Solution:

Due to the surface tension, a liquid drop tends to assume a spherical shape to minimise the surface area.

QUESTION: 15

The freezer in a refrigerator is located at the top section so that

Solution:

Because of the entire chamber of the refrigerator is cooled quickly due to convection.

QUESTION: 16

Consider the following statements and select the correct code.
Assertion (A): The velocity of sound in air increased due to the presence of moisture in it.
Reason (R): The presence of moisture in air lowers the density of air.

Solution:

The velocity of sound in air increases as the humidity increases.

QUESTION: 17

Which of the following properties is not possible in case of X-rays?

Solution:

Due to high penetrating power, the properties of interference, diffraction and polarization are not possible in X-ray.

QUESTION: 18

Which of the following is not correctly matched?

Solution:

Galvanometers are electrical devices used for the detection or measurement of the electric currents

QUESTION: 19

If alpha, beta and gamma rays carry same momentum, which has the longest wavelength?

Solution:

When alpha, beta and gamma rays carry same momentum, then all have same wavelength as λ = h / P  where λ = wavelength, P = momentum and h = Plank’s constant (= 6.62 × 10– 34 Js).

QUESTION: 20

Consider the following statements :
The fraction of a ball floating inside the liquid depends upon
1. density of the liquid
2. mass of the ball
3. density of the ball

Q. Which of the statements given above are correct?

Solution:

The fraction of a ball floating inside the liquid depends only upon density of the liquid and the ball.

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