Physics Questions

Q:

Which is best used as a sound absorbing material in partition walls ?

A) Stone chips B) Steel
C) Glass - wool D) Glass pieces
 
Answer & Explanation Answer: C) Glass - wool

Explanation:

Materials that do not transfer mechanical energy well. These tend to be soft,flexible, low density, and with high surface area to linear area ratios.

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Q:

Skating on ice is possible because 

A) the surface of ice is smooth B) ice is cold
C) the pressure on the ice due to skate melts the ice by lowering its melting point forming a thin film of water D) the pressure on the ice due to skate raises its melting point
 
Answer & Explanation Answer: C) the pressure on the ice due to skate melts the ice by lowering its melting point forming a thin film of water

Explanation:

Here is a case of  lowering of melting point of ice with increase of pressure

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Q:

Ultrasonic waves are used for stirring liquid solutions because they 

A) do not produce noise during the operation B) are easy to produce
C) can produce perfectly homogeneous solutions D) do not produce chemical reactions in the solution
 
Answer & Explanation Answer: C) can produce perfectly homogeneous solutions

Explanation:
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Q:

If lift is going up with acceleration, the apparent weight of a body is

A) may be more or less than true weight B) more than the true weight
C) less than the true weight D) equal to the true weight
 
Answer & Explanation Answer: B) more than the true weight

Explanation:
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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 minimum number of Non zero non collinear vectors required to produce a zero vector is

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

Explanation:
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Q:

Pieces of camphor placed on water move about rapidly. This is because of

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

Explanation:

The Camphor slowly dissolves in the water lowering the latter's surface tension in the immediate neighbourhood. The stronger pull exerted by the uncontaminated portion of water brings about a movement of the surface and the camphor particles are carried along with it. When after sometime the whole surface settles for the reduced tension, the movement of the camphor too short.

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Q:

Mirage is an example of

A) Reflection of light & Refraction of light B) Dispersion of light
C) Total Internal Reflection D) Refraction of light & Total Internal Reflection of light
 
Answer & Explanation Answer: D) Refraction of light & Total Internal Reflection of light

Explanation:

A Mirage is a naturally occurring optical phenomenon in which light rays bend to produce a displaced image of distant objects or the sky.




      • It is caused due to Total internal Reflection.

 

      • It is an optical illusion observed in deserts or hot summer days due to which a person sees a pond of water some distance ahead of him in which the surrounding objects appear inverted.

Mirage_is_an_example_of1556276063.jpg image


How Mirage Forms::

 

1. The temperature of other layers of atmosphere goes on decreasing as we go up.
2. Therefore density and refractive index of air changes as one goes up.
3. Thus a ray of light,gets refracted more and more away from the normal.
4. At a particular angle when a ray of light exceeds critical angle, total internal reflection takes place and ray of light gets reflected in the same medium.
5. when the reflected ray reaches our eye, it appears as coming from tree or sky .
6. Hence the inverted image of tree creates an impression from a pond of water.

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