Physics
A copper wire of radius r and length l has a resistance of R. A second copper wire with radius 2r and length l is taken and the two wires are joined in a parallel combination. The resultant resistance of the parallel combination of the two wires will be

R/5
4 R/5
5 R
5 R/4

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Physics
Stars twinkle because

the intensity of light emitted by them changes with time.
the distance of the stars from the earth changes with time.
None of these
the refractive index of the different layers of the earth's atmosphere ch

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Physics
It takes much longer to cook food in the hills than in the plains, because

due to low atmospheric pressure on the hills, the water boils at a temperature higher than 100oC and therefore water takes longer to boil
in the hills the atmospheric density is low and therefore a lot of heat is lost to the atmosphere
in the hills the humidity is high and therefore a lot of heat is absorbed by the atmosphere leaving very little heat for cooking
n the hills the atmospheric pressure is lower than that in the plains and therefore water boils at a temperature lower than 100oC causing an increase in cooking time

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