Physics - Thermal Properties of Matter
Exam Duration: 45 Mins Total Questions : 30
Heat given to a system can be associated with
- (a)
kinetic energy of random motion of molecules
- (b)
kinetic energy of orderly motion of molecules
- (c)
total kinetic energy of random and orderly motion of molecules
- (d)
kinetic energy of random motion in some cases and kinetic energy of orderly motion in other
At what temperature (in o C), the fahrenheit and celsius scale gives same reading?
- (a)
40
- (b)
-40
- (c)
8
- (d)
-8
A bimetallic strip is made of aluminium and steel \(\left( { \alpha }_{ Al }>{ \alpha }_{ steel } \right) \) on heating, the strip will
- (a)
remain straight
- (b)
get twisted
- (c)
get twisted
- (d)
bend with aluminium on concave side
If a piece of metal is heated to temperature \(\theta \) and then allowed to cool in a room which is at temperature \(\theta _0\), the graph between the temperature T of the metal and time t will be closed to
- (a)
- (b)
- (c)
- (d)
The radius of metal sphere at room temperature T is R and the coefficient of linear expansion of the metal is \(\alpha \) . The sphere is heated a little by a temperature T so that, new temperature is \(T+\Delta T.\) The increase in volume of sphere is approximately
- (a)
\(2\pi R\alpha \Delta T\)
- (b)
\(\pi { R }^{ 2 }\alpha \Delta T\)
- (c)
\(4\pi { R }^{ 3 }\alpha \Delta T/3\)
- (d)
\(4\pi { R }^{ 3 }\alpha \Delta T\)
Which one of the following would raise the temperature of 40 g of water at 20o C most mixed with?
- (a)
20 g of water at 40o C
- (b)
30 g of water at 30o C
- (c)
10 g of water at 60o C
- (d)
4 g of water at 100o C
A black body is at 2000 K, it emits maximum energy at a wavelength 1\(\mu m\) . The temperature, it emits at wavelength of 2\(\mu m\) is
- (a)
1000 K
- (b)
2000 K
- (c)
500 K
- (d)
100 K
A star emits wavelength 289.8 nm of maximum intensity. Then, radiant intensity of state is \((\sigma =5.67\times { 10 }^{ -8 }W/{ m }^{ 2 }/{ k }^{ 4 },\) Wein's constant, b=2898X10-6 mK)
- (a)
5.67X1016 W/m2
- (b)
5.67X1014 W/m2
- (c)
5.67X1010 W/m2
- (d)
5.67X108 W/m2
Wein's displacement law for emission of radiation can be written as
- (a)
\({ \lambda }_{ max }\) is inversely proportional to square of absolute temperature (T2)
- (b)
\({ \lambda }_{ max }\) is inversely proportional to absolute temperature (T)
- (c)
\({ \lambda }_{ max }\) is directly proportional to absolute temperature (T)
- (d)
\({ \lambda }_{ max }\) is inversely proportional to square of absolute temperature (T2 )
If temperature of black body increases from 300 K to 900 K, then the rate of energy radiation increase by
- (a)
81
- (b)
3
- (c)
9
- (d)
2
A black body radiate energy at rate of X W/m2 at a high temperature of TK. When temperature is reduced to \(\left( \frac { T }{ 2 } \right) K\) , the radiant energy is
- (a)
\(\frac { X }{ 16 } \)
- (b)
\(\frac { X }{ 4 } \)
- (c)
\(\frac { X }{ 2 } \)
- (d)
\(2X\)
A black body radiates heat energy at the rate of 3X106 W at 127oC. The temperature at which it would radiate heat energy at 243X106 W is
- (a)
1000 K
- (b)
1200 K
- (c)
1400 K
- (d)
1600 K
Newton's law of cooling hold's good only, if the temperature difference between the body and the surrounding is
- (a)
less than 40o C
- (b)
more than 50o C
- (c)
less than 100o C
- (d)
more than 100o C
A clock with a steel pendulum keeps correct time at 25oC. What will be the error in second per day, if room temperature is 35oC? (coefficient of linear expansion, \({ \alpha }_{ steel }=5\times { 10 }^{ -5 }{ C }^{ -1 })\)
- (a)
43.2 s gained
- (b)
43.2 s lost
- (c)
21.6 s gained
- (d)
21.6 s lost
If a liquid cools from 70oC to 55oC in 5 min and then to 45o C in 10 min, then temperature of surrounding is
- (a)
50oC
- (b)
60oC
- (c)
25oC
- (d)
20oC
The thickness of ice on a lake is 10 cm and the temperature of air is -10oC. If rate of cooling of water inside lake is 20000 cal min-1 through each square metre surface, then K for ice is
- (a)
14
- (b)
10
- (c)
3
- (d)
4
If a cylinder of radius R having thermal conductivity K1 is surrounded by other cylindrical shell of radius 2R having thermal conductivity K2 . Two ends are maintained at two different temperatures. In steady state, the effective thermal conductivity of system is (assume no heat loss)
- (a)
\(\frac { { k }_{ 1 }+{ 4k }_{ 2 } }{ 4 } \)
- (b)
\(\frac { { k }_{ 1 }+{ 3k }_{ 2 } }{ 4 } \)
- (c)
\(\frac { { 4k }_{ 1 }+{ k }_{ 2 } }{ 4 } \)
- (d)
\(\frac { { 3k }_{ 1 }+{ k }_{ 2 } }{ 4 } \)
Two rods X and Y having equal lengths. Then, cross-sectional area are Ax and Ay and thermal conductivities Kx and Ky . When the temperature at ends of each rod are are Tx and Ty respectively, the rate of flow of heat through X and Y will b, if equal
- (a)
\(\frac { { A }_{ x } }{ { A }_{ y } } =\frac { { K }_{ y } }{ { K }_{ x } } \)
- (b)
\(\frac { { A }_{ x } }{ { A }_{ y } } =\frac { { K }_{ y } }{ { K }_{ x } } \times \frac { { T }_{ y } }{ { T }_{ x } } \)
- (c)
\(\frac { { A }_{ x } }{ { A }_{ y } } =\sqrt { \frac { { K }_{ y } }{ { K }_{ x } } } \)
- (d)
\(\frac { { A }_{ x } }{ { A }_{ y } } ={ \left( \frac { { K }_{ y } }{ { K }_{ x } } \right) }^{ 2 }\)
Match the laws given in Column I, with their formula in column II and select the correct option in the choices given below.
| Column I | Column II | ||
| A. | Newton's law of cooling | 1. | \({ \lambda }_{ m }.T=constant\) |
| B. | Calorimetry | 2. | \(\frac { dQ }{ dt } =K\Delta T\) |
| C. | Wein's displacement law | 3. | \({ m }_{ 1 }{ s }_{ 1 }\left( { \theta }_{ 1 }-\theta \right) ={ m }_{ 2 }{ s }_{ 2 }\left( \theta -{ \theta }_{ 2 } \right) \) |
- (a)
A B C 3 1 2 - (b)
A B C 1 2 3 - (c)
A B C 2 3 1 - (d)
A B C 3 2 1
A liquid in a breaker has temperature \(\theta (t)\) at time t and \({ \theta }_{ 0 }\) is temperature of surroundings, then according to Newton's law of cooling the correct graph between \({ log }_{ e }\left( \theta -{ \theta }_{ 0 } \right) \) and t is
- (a)
- (b)
- (c)
- (d)
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