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Test: Physics - 1

20 Questions MCQ Test Science & Technology for UPSC CSE | Test: Physics - 1

Description

Attempt Test: Physics - 1 | 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

An iron needle sinks in water whereas a ship made of iron floats on it because

A.
the edge of the needle is pointed
B.
the ship is flat
C.
the ship is driven by powerful engine
D.
specific gravity of the needle is greater than that of water displaced by it.

Solution:

Because the specific gravity of the needle is greater than that of water displaced by it. Specific gravity (or relative density) = Density of the substance / Density of the water at 4°C The average density of iron needle is greater than water, therefore, it sinks.

QUESTION: 2

The cloudy nights are warmer than clear nights because

A.
clouds prevent escape of radiation of heat from the ground and the air.
B.
absorb sunlight in the day and radiate the same in night.
C.
clouds make the atmosphere damp and generate heat.
D.
clouds obstruct the movement of air which creates heat.

Solution:

The cloudy nights are warmer because clouds prevent escape of radiation of heat from the ground and the air.

QUESTION: 3

Food gets cooked faster in a pressure cooker because

A.
water starts boiling at a higher temperature due to high pressure
B.
water starts boiling at a lower temperature due to high pressure
C.
water boils only at 100°C but the heat content is higher at high pressure
D.
convection currents are set inside the cooker

Solution:

At that pressure, water boils at 121°C (250°F). That means food can cook at a much higher temperature than it ever could at atmospheric pressure—and since cooking reactions speed up at higher temperatures, your food cooks faster.

QUESTION: 4

It is more comfortable to wear white cloths in summer because

A.
they reflect heat falling on them.
B.
they radiate heat tansferred from the body.
C.
they absorb perspiration.
D.
they are soothing to the eye.

Solution:

The white clothes reflect heat falling on them in summer and they absorb the least from the sun.

QUESTION: 5

Of the two bulbs in a house, one glows brighter than the other. Which of the following statements is correct?

A.
The brightness does not depend on resistance.
B.
Both the bulbs have the same resistance.
C.
The brighter bulb has larger resistance.
D.
The dimmer bulb has larger resistance.

Solution:

The dimmer bulb has larger resistance than the brighter one. Power of the bulb ∝ 1 / Resistance Resistance is the obstruction offer to the flow of current.

QUESTION: 6

A fluorescent tube is preferred to an electric bulb because

A.
it has a larger light emitting surface.
B.
voltage fluctuations do not affect it.
C.
in a tube electrical energy is almost converted into light.
D.
None of these

Solution:

In a fluorescent tube, electrical energy is almost converted into light. The inner wall of the fluorescent tube is coated with phosphorus which immediately transformed into bright light.

QUESTION: 7

Consider the following statements in respect of a jet engine and a rocket:
1. A jet engine uses the surrounding air for its oxygen supply and so is unsuitable for motion in space.
2. A rocket carries its own supply of oxygen in the gas form as a fuel.

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

A.
1 only
B.
2 only
C.
Both 1 and 2
D.
Neither 1 nor 2

Solution:

In respect of a jet engine and a rocket, both the given statements are correct.

QUESTION: 8

The leaning tower of Pisa does not fall because

A.
it is tappered at the top.
B.
it covers a large base area.
C.
its centre of gravity remains at the lowest position.
D.
the vertical line through the centre of gravity of the tower falls within the base.

Solution:

Because the vertical line through the centre of gravity of the tower falls within the base.

QUESTION: 9

Electronic motors operating at low voltages tend to burn out because

A.
they draw more current which is inversely proportional to the voltage.
B.
they draw more current which is inversely proportional to the square root of the voltage.
C.
they draw heat proportional to V^2.
D.
low voltage sets in electrical discharge.

Solution:

Electronic motors draw more current which is inversely proportional to the voltage, therefore, more heat H = I²Rt is generated.

QUESTION: 10

If the doors of a refrigerator are left open for a few hours, the room temperature will

A.
decrease
B.
increase
C.
remain the same
D.
decrease only in the area in the vicinity of the refrigerator

Solution:

If the doors of a refrigerator are left open for a few hours, the room temperature will increases. It is because system releases heat to the surroundings.

QUESTION: 11

If a rock is brought from the surface of the moon to the earth, then

A.
its mass will change.
B.
its weight will change but not its mass.
C.
both mass and weight will change.
D.
both mass and weight will remain the same.

Solution:

If a rock is brought from the surface of the moon to the earth, its weight will change but not its mass. Mass is a invariant physical quantity whereas weight of a body (w = mg) is variable as the value of acceleration due to gravity (g) changes.

QUESTION: 12

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

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

Solution:

Wavelength is the distance between two consecutive crests or troughs and 1 angstrom = 10–¹⁰m, joule is the unit of energy. Intensity of sound is measured in decibel. Frequency is measured in hertz (Hz).

QUESTION: 13

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

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

Solution:

The unit of temperature is kelvin, power is measured in watt, pressure in pascal and force in newton.

QUESTION: 14

Which one of the following statements is not true about cosmic rays?

A.
They have very high frequency.
B.
They have very high wavelength.
C.
They are made of highly energetic charged particles.
D.
They originate from the sun.

Solution:

Cosmic rays have very high frequency >10²³ Hz and wavelength <10^–24 m.

QUESTION: 15

Pendulum clocks become slow in summer because

A.
days in summer are large.
B.
of the friction in the coil.
C.
the length of the pendulum increases.
D.
the weight of the pendulum changes.

Solution:

Pendulum clocks become slow in summer because the length of the pendulum increases. Increase in length ∆l = l_o α ∆T where l_o= original length, α = coefficient of linear expansion and ∆T = change in temperature.

QUESTION: 16

Consider the following statements and select the correct code:
Assertion (A): A piece of ice added to the drink cools it.
Reason (R): Ice takes latent heat from the drink for melting resulting in the cooling of the drink.

A.
Both A and R are true, and R is the correct explanation of A.
B.
Both A and R are true, but R is not the correct explanation of A.
C.
A is true, but R is false.
D.
A is false, but R is true.

Solution:

A piece of ice added to the drink cool it because ice takes latent heat from the drink for melting resulting in the cooling of the drink.

QUESTION: 17

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

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

Solution:

Revolver was discovered by Colt. Dynamite was discovered by Alfred Nobel. Law of cooling was discovered by Newton and law of pressure by Pascal.

QUESTION: 18

The atmosphere exerts enormous pressure on us. But, we don’t feel it because

A.
our blood exerts a pressure slightly more than that of the atmosphere.
B.
we are used to it.
C.
our bones are very strong and can withstand the pressure.
D.
the surface area of our head is very small.

Solution:

We don’t feel the atmospheric pressure because our blood exerts a pressure slightly more than that of the atmosphere.

QUESTION: 19

Which one of the following statements is not true for a person suffering from hypermetropia?

A.
The person can see far objects distinctly.
B.
The focal length of the lens is large.
C.
The image of the close object is focussed behind the retina.
D.
A concave lens is used to correct this defect.

Solution:

Hypermetropia is corrected by using a convex lens.

Myopia is corrected by concave lens.

QUESTION: 20

Consider the following statements and select the correct answer using the codes given below:
Assertion (A): If ice collects on the freezer, the cooling in the refrigerator is affected adversely.
Reason (R): Ice is a poor conductor.