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Q:

Hot water is poured simultaneously in four metallic tumblers painted outside with different paints. After some time the water will be found to have cooled most in the tumbler painted.

A) rough white B) rough black
C) shining white D) shining black

Answer:   B) rough black

Explanation:

Black surfaces are good emitters of heat. If the black surface is rough too, the emitting will be better. Shinning surfaces reflect black radiation . So if the black surface is also shining the effectiveness of emitting heat is lessened.

Subject: Physics
Q:

The capacity of a pure capacitor is 1 farad. In D.C circuit, its effective resistance will be

A) Zero B) Infinite
C) 1 Ohm D) 1/2 Ohm
 
Answer & Explanation Answer: B) Infinite

Explanation:
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Q:

A convex mirror is used to form an image of a real object. The image

A) is diminished in size B) is erect
C) always lies between the pole and the focus D) all of the above
 
Answer & Explanation Answer: D) all of the above

Explanation:
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Q:

The quality of sound produced by an instrument depends on the

A) Frequency B) Intensity
C) Number of overtones D) None of these
 
Answer & Explanation Answer: C) Number of overtones

Explanation:
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Q:

In the electrical circuit of a house, the fuse acts as

A) a load B) a thermopile
C) a safety device D) a step down device
 
Answer & Explanation Answer: C) a safety device

Explanation:
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Q:

The direction of heat flow between two objects depends on

A) Their masses B) Their heat contents
C) Their temperatures D) Whether they are in solid, liquid or gaseous state
 
Answer & Explanation Answer: C) Their temperatures

Explanation:

Heat always flows from a body at higher temperature to a body at a lower temperature.

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