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Q:

Two metallic plate of equal thickness and coefficient thermal conductivity K1 and K2 put together face to face. A common plate is constructed. What is equivalent K? 

A) K1k2/k1+k2 B) 2k1k2/k1+k2
C) K1+k2/k1k2 D) None

Answer:   B) 2k1k2/k1+k2



Explanation:

We know that,

 

The equivalent K =  L1 + L2L1K1+L2K2

 

where L1 & L2 are plate1 & Plate2 thicknesses, K1 & K2 are coefficient thermal conductivity of plate1 & Plate2 respectively.

 

But here L1 = L2 = L (say)

 

Then K = L+L/(L/K1 + L/K2)  =  2K1K2K1+K2

Subject: Physics
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Q:

Electric power is measured in units of

A) Volt B) Joule
C) Watt D) Ampere
 
Answer & Explanation Answer: C) Watt

Explanation:

Electric power is the rate per unit time, at which electrical energy is transferred by an electric circuit. The power of electricity is measured in watts and kilo watts.

1 Watt is the unit of electrical power equal to one ampere under the pressure of one volt.

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1 45
Q:

Sound becomes hazardous noise pollution at decibels?

A) above 120 db B) above 80 db
C) above 50 db D) above 30 db
 
Answer & Explanation Answer: A) above 120 db

Explanation:

Sound intensity is measured in decibels(db). Sound pollution above 120 db becomes more hazardous and have adverse affects on human life. 

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0 60
Q:

Heat transfer by radiation mainly depends upon

A) Kind and extent of its surface B) Its temperature
C) Nature of the body D) All of the above
 
Answer & Explanation Answer: D) All of the above

Explanation:

Heat transfer through radiation takes place in form of electromagnetic waves mainly in the infrared region. It depends on nature of the body, its temperature and kind & extent of its surface.

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0 25
Q:

The combined gas law relates which of the following?

A) Volume & Temperature B) Temperature & Pressure
C) Volume & Pressure D) Volume, Temperature & Pressure
 
Answer & Explanation Answer: D) Volume, Temperature & Pressure

Explanation:

The combined gas law states that the ratio between the pressure-volume product and the temperature of a system remains constant.

 

Hence it depends on all the three Volume, Temperature & Pressure.

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1 61
Q:

Land is considered a resource because it

A) is used to produce things B) requires labor to be useful
C) is always available to use D) costs little or nothing to use
 
Answer & Explanation Answer: A) is used to produce things

Explanation:

Land is considered as an important resource because it is useful in producing many things. For example, in agriculture, land is used for cultivating the crop, in industrial use, it is used for constructing factories and to make products that we use.

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0 44
Q:

As water is cooled from 4 deg C to 0 deg C, its density

A) increases B) decreases
C) remains same D) None of the above
 
Answer & Explanation Answer: B) decreases

Explanation:

As water is cooled from 4 deg C to 0 deg C, the water reaches its freezing point and starts forming ice crystals. Then the volume of that ice cubes increases and its density decreases. Hence, it is the reason that ice will float on water as ice has less density than the water.

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5 149
Q:

The GPS device in an automobile uses which communication channel?

A) Satellite B) Microwave
C) Radio frequency D) Infrared
 
Answer & Explanation Answer: A) Satellite

Explanation:

All automobiles uses satellite communication channel for their GPS devices.

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1 63
Q:

What type of simple machine is an axe?

A) Lever B) Wedge
C) Both A & B D) The screw
 
Answer & Explanation Answer: C) Both A & B

Explanation:

The simple machine Axe is made up of both the lever arm and a wedge.

                              what_type_of_simple_machine_is_an_axe1536562753.png image

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