1
AIPMT 2012 Prelims
+4
-1
Liquid oxygen at 50 K is heated to 300 K at constant pressure of 1 atm. The rate of heating is constant. Which one of the following graphs represents the variation of temperature with time ?
A
B
C
D
2
AIPMT 2012 Prelims
+4
-1
If the radius of a star is R and it acts as a black body, what would be the temperature of the star, in which the rate of energy production is Q?
A
$${Q \over {4\pi {R^2}\sigma }}$$
B
$${\left( {{Q \over {4\pi {R^2}\sigma }}} \right)^{ - 1/2}}$$
C
$${\left( {{{4\pi {R^2}Q} \over \sigma }} \right)^{1/4}}$$
D
$${\left( {{Q \over {4\pi {R^2}\sigma }}} \right)^{1/4}}$$
3
AIPMT 2010 Prelims
+4
-1
A cylindrical metallic rod in thermal contact with two reservoirs of heat at its two ends conducts an amount of heat Q in time t. The metallic rod is melted and the material is formed into a rod of half the radius of the original rod. What is the amount of heat conducted by the new rod, when placed in thermal contact with the two reservoirs in time t?
A
$${Q \over 4}$$
B
$${Q \over {16}}$$
C
2Q
D
$${Q \over 2}$$
4
AIPMT 2010 Prelims
+4
-1
The total radiant energy per unit area, normal to the direction of incidence, received at a distance R from the centre of a star of radius r, whose outer surface radiates as a black body at a temperature TK is given by
A
$${{\sigma {r^2}{T^4}} \over {{R^2}}}$$
B
$${{\sigma {r^2}{T^4}} \over {4\pi {R^2}}}$$
C
$${{\sigma {r^2}{T^4}} \over {{R^4}}}$$
D
$${{4\pi \sigma {r^2}{T^4}} \over {{R^2}}}$$
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