Physics Questions

Q:

What is the effective resistance (in Ω) of two resistors 21 Ω and 28 Ω connected in parallel?

 

A) 49 B) 24
C) 12 D) 98
 
Answer & Explanation Answer: C) 12

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Q:

What is the heat released by a heating filament rated 20 W when it is kept on for 2 seconds?

 

A) 40 B) 10
C) 80 D) 20
 
Answer & Explanation Answer: A) 40

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Q:

Which of the following is not true about Frictional force?

 

A) Friction is the force which opposes the relative motion of two surfaces in contact B) The force of friction that acts when a body is moving (sliding) on a surface is called sliding friction
C) Friction in machines wastes energy and also causes wear and tear D) Rolling friction is much more than sliding friction, the use of ball bearings in a machine considerably reduces friction
 
Answer & Explanation Answer: D) Rolling friction is much more than sliding friction, the use of ball bearings in a machine considerably reduces friction

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Q:

Rocket works on the principle of conservation of

 

A) Momentum B) Mass
C) Velocity D) Energy
 
Answer & Explanation Answer: A) Momentum

Explanation:

Rocket works on the principle of conservation of momentum. The rockets gain momentum equal to the momentum of the gas expelled from the engine, but in the opposite direction.

 

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Q:

Working of safety fuses depends upon

1. magnetic effect of the current

2. chemical effect of the current

3. magnitude of the current

4. heating effect of the current

Select the correct answer using the code given below.

 

A) 1, 2, 3 and 4 B) 1, 2 and 3 only
C) 3 and 4 only D) 4 only
 
Answer & Explanation Answer: C) 3 and 4 only

Explanation:

An electric fuse is a device which is used to limit the current in an electric circuit. The fuse safeguards the circuit and the electrical appliances from being damaged.

The fuse wire is generally an alloy of lead and tin. It has a low melting point and breaks the circuit if the current exceeds a safe value. The thickness and length of the fuse wire depends on the maximum current allowed through the circuit.

It is connected in series in the beginning of the electric circuits.

If too many electrical appliances of high power rating (like electric iron, water heater etc) are switched on at the same time, they draw an extremely large current from the circuit. This condition is called overloading and it can cause overheating of the wiring and lead to a fire. (heating effect and magnitude of the current)

 

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Q:

Which one of the following is applicable to collision-coalescence process of precipitation?

 

A) Clouds which do not extend beyond the freezing level B) Clouds which extend beyond the freezing level
C) All types of clouds D) Cirrocumulus cloud
 
Answer & Explanation Answer: A) Clouds which do not extend beyond the freezing level

Explanation:

In colder clouds: droplets formed by Bergeron mechanism. But, in many parts of the world the air is too warm for ice crystals to form. This being the case, rain and snow cannot develop following the Bergeron Process. Instead, tiny droplets form as they collide into one another creating larger and larger droplet, this is known as collision-coalescence process. So, warmer clouds are associated with this keyword.

 

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Q:

Calculate the pressure (in Pa) if a thrust of 1000 N is applied to an area of 5 sq.m.

 

A) 200 B) 50
C) 100 D) 25
 
Answer & Explanation Answer: A) 200

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Q:

Which of the following statements is/are INCORRECT?

 

A. The value of G on the moon is equal to that on the earth.

B. 26.68 x 10-11 N is the force of gravitation between two point masses of 2 kg and 2kg kept 1 m apart.

C. Newton's law of gravitation is valid in the laboratory only.

D. Force is inversely proportional to the square of the distance between two bodies.

 

A) B, C and D B) C and D only
C) Only C D) Only A
 
Answer & Explanation Answer: C) Only C

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