Physics Questions

Q:

The basic reason for the extraordinary sparkle of suitably cut diamond is that

A) it has well defined cleavage planes B) it has a very high transparency
C) it has a very high refractive index D) it is very hard
 
Answer & Explanation Answer: C) it has a very high refractive index

Explanation:
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Q:

Air pressure is usually highest when the air is 

A) warm and moist B) cool and dry
C) warm and dry D) cool and moist
 
Answer & Explanation Answer: D) cool and moist

Explanation:

Both warmth and moisture reduce the density of air and hence its pressure is high.

                                  Air_pressure_is_usually_highest_when_the_air_is1558073685.png image

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Q:

Sound following a flash of lightning is called

A) Stoning B) Bolting
C) Thunder D) Cloud clash
 
Answer & Explanation Answer: C) Thunder

Explanation:

The Sound Following the flash of lighting is because of Thunder.

 

Lightning is seen earlier than thunder because light travels much faster than sound.

 

The roar of thunder is the result of a shock wave produced when lightning super-heats the air through which it passes, causing that air to expand very rapidly. This rapid expansion of air creates a shock wave that travels outward at close to the speed of sound.

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Q:

The purpose of choke in tube light is

A) Induce high voltage B) Induce low resistance
C) Induce high resistance D) Induce low voltage
 
Answer & Explanation Answer: A) Induce high voltage

Explanation:

When the switch is ON, in a tube light choke is nothing but the coil/ballast ( inductor) which is used to induce the high voltage across it. as we know that inductor has property to induce high voltage for the brief period of time, this high voltage is required to ionize the gases in the starter.

Then gas inside the starter gets ionized due to this full voltage and heats the bimetallic strip that is caused to be bent to connect to the fixed contact. Current starts flowing through the starter. Although the ionization potential of the neon is the little bit more than that of the argon but still due to small electrode gap high voltage gradient is appeared in the neon bulb and hence glow discharge is started first in a starter.

As voltage gets reduced due to the current causes a voltage drop across the inductor, the strip cools and breaks away from the fixed contact. At that moment a large L di/dt voltage surge comes across the inductor at the time of breaking.

This high valued surge comes across the tube light electrodes and strikes penning mixture (mixture argon gas and mercury vapor).

Gas discharge process continues and current gets the path to flow through the tube light gas only due to low resistance as compared to the resistance of starter.

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Q:

When a bottle of perfume is opened in one corner of a room the smell spreads soon throughout the room. This is an example of

A) surface tension B) capillarity
C) viscosity D) diffusion
 
Answer & Explanation Answer: D) diffusion

Explanation:

Diffusion is the spreading  - mixing of gases through molecular motion.

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Q:

Optical fiber works on the principle of

A) Scattering B) interference
C) total internal reflection D) refraction
 
Answer & Explanation Answer: C) total internal reflection

Explanation:

Optical_fiber_works_on_the_principle_of1556277954.jpg image

 

Optical fiber works on the principle of total internal reflection.

 


The Total Internal Reflection is the phenomenon in which the complete reflection of a light ray reaching an interface with a less dense medium when the angle of incidence exceeds the critical angle.

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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:

The rate of change of linear momentum of a body falling freely under gravity is equal to it's ____ ?

A) Kinetic Energy B) Weight
C) Potential Energy D) Impulse
 
Answer & Explanation Answer: B) Weight

Explanation:

Rate of change of impulse equals the force . In case of freely falling body the only force is the weight.

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