Revision Series | Science | General Science | 54

December 16, 2023

The form of carbon known as graphite

(A) Is harder than diamond
(B) Contains a higher percentage of carbon than diamond
(C) Is a better electrical conductor than diamond
(D) Has equal carbon-to-carbon distances in all directions

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Answer- C

Assertion : Velocity is a derived physical quantity.
Reason : Velocity cannot be derived from the fundamental physical quantities.

(A) If both Assertion and Reason are correct and Reason is the correct explanation of Assertion.
(B) If both Assertion and Reason are correct, but Reason is not the correct explanation of Assertion.
(C) If Assertion is correct but Reason is incorrect.
(D) If Assertion is incorrect but Reason is correct.

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Answer- C

If a ship moves from freshwater into seawater, it will

(A) Sink completely
(B) Sink a little bit
(C) Rise a little higher
(D) Remain unaffected

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Answer- C

The correct answer is rise a little higher.

The buoyant force is an upward force on an object that is wholly or partially immersed in a fluid.

Due to the force of buoyancy, a body partially or wholly immersed in a liquid tends to lose its weight, that is, it appears to be lighter.

When a moving bus suddenly applies brakes, the passengers sitting in it fall in the forward direction. This can be explained by

(A) The theory of relativity
(B) Newton’s first law
(C) Newton’s second law
(D) Newton’s third law

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Answer- B

This can be explained by Newton’s first law. This is true because of the law of inertia when the bus was moving with some constant velocity hence passengers will also move with the bus.

Match List I (Units) with List II (Physical quantity) and select the correct answer using the codes given below the lists.
List I (Units) = List II (Physical quantity)
(A) Watt = 1. Electric charge
(B) Tesla = 2. Power
(C) Coulomb = 3. Luminous intensity
(D) Candela = 4. Magnetic field

(A) A-1, B-4, C-2, D-3
(B) A-2, B-1, C-3, D-4
(C) A-1, B-2, C-4, D-3
(D) A-2, B-4, C-1, D-3

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Answer- D

The pressure exerted on the ground by a man is greatest

(A) When the lies down in the ground
(B) When the stands on the toes of one foot
(C) When the stands with both foot flat on the ground
(D) All of the above yield the same pressure

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Answer- B

As such, the greatest pressure corresponds to the least surface area in contact with the ground. The least surface area is when the person stands on his toes.
The pressure exerted on the ground by a man is greatest when (c) He stands on the toes of one foot.

Light Emitting Diode (LED) converts

(A) Light energy into electrical energy
(B) Electrical energy into light energy
(C) Thermal energy into light energy
(D) Mechanical energy into electrical energy

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Answer- B

It is an optical semiconductor device that emits light when voltage is applied means it converts electrical energy into light energy.

When Light Emitting Diode (LED) is forward biased, the free electrons from the n-side and the holes from the p-side are pushed towards the junction.

Regarding plants, consider the following sentences:
1. All plants synthesize their food themselves.
2 . Plants obtain nitrogen through roots present in the soil.
Which of the above assertions is/are correct?

(A) 1 only
(B) 2 only
(C) Both 1 and 2
(D) Neither 1 nor 2

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Answer- B

There are some plants which do not have chlorophyll. They cannot synthesise food.
Like humans and animals such plants depend on the food produced by other plants.
They use the heterotrophic mode of nutrition. For example: Cuscuta (Amarbel).
Plants cannot absorb nitrogen in gaseous form.
Soil has certain bacteria that convert gaseous nitrogen into a usable form and release it into the soil. This is absorbed by the plants along with water.

A moderator is used in nuclear reactors in order to

(A) Slow down the speed of the nuetrons
(B) Acceleerate the neutrons
(C) Increase the number of neutrons
(D) Decrease the number of neutrons

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Answer- A

A moderator is a substance used to reduce the speed of neutrons.
Therefore, it can sustain nuclear chain reaction in the reactor.
It can increase the probability of collision between neutrons and fuel rods.
Water, heavy water and graphite are the examples for moderators.