CBSE
Multiple Choice QuestionsAccording to Newton's law of cooling, the rate of cooling of a body is proportional to ()n 1, where Δθ is the difference of the temperature of the body and the surroundings and n is equal to
2
3
4
1
A body has initial temperature of 80°C. It cools by radiation process. In 5 minutes, it cools down to 64°C and in 10 minutes, it cools down to 52C. The temperature of surrounding is:
8°C
16C
32C
24C
A beaker is completely filled with water at 4°C. It will overflow if:
heated above 4°C
cooled below 4°C
both heated and cooled above and below 4°C respectively
none of these
In which process the rate of transfer of heat is maximum?
Conduction
Radiation
Convection
In all three heat is transferred with the same speed
The temperature of the black body increases from T to 2T. The factor by which the rate of emission will increase is
4
2
16
8
If the temperature difference on the two sides of a wall increases from 100°C to 200°C, its thermal conductivity :
remains unchanged
is doubled
is halved
becomes four times
Calculate the amount of heat (in calories) required to convert 5g of ice at 0°C to steam at 100°C
3100
3200
3600
4200
Let there be four articles having colours blue, red, black and white. When they are heated together and allowed to cool, which article will cool at the earliest?
Blue
Red
Black
White
A piece of red glass when heated in dark to the red hot state will appear to be :
White
Red
Green
Invisible
A black body at 227°C radiates heat at the rate of 7 cal/cm2 -s. At a temperature of 727°C. the rate of heat radiated in the same units will be
80
60
50
112
