Multiple Choice QuestionsA point source emits sound equally in all directions in a non-absorbing medium. Two points P and Q are at distance of 2m and 3m respectively from the source. The ratio of the intensities of the waves at P and Q is
9:4
2:3
3:2
4:9
Which of the following circular rods, (given radius r and length l) each made of the same material and whose ends are maintained at the same temperature will conduct most heat?
r = 2ro, l = 2lo
r = 2ro, l = lo
r = ro, l = lo
r = ro, l = lo
The circular motion of a particle with constant speed is
simple harmonic but not periodic
periodic and simple harmonic
neither periodic nor simple harmonic
periodic but not simple harmonic
A particle executing simple harmonic motion of amplitude 5 cm has maximum speed of 31.4 cm/s. The frequency of its oscillation is
3 Hz
2 Hz
4 Hz
1 Hz
Which of the following processes is reversible?
Transfer of heat by radiation
Electrical heating of a nichrome wire
Transfer of heat by conduction
Isothermal compression
A.
Transfer of heat by radiation
When two bodies are at different temperatures and seperated by distance, the heat transfer between them is called as radiation heat transfer. A reversible process in which system and surroundings can be restored to the initial state from the final state without producing any changes in the thermodynamic properties called revrsible process.
(a) It is the process by which heat is transmitted from one place to another without heating the intervening medium. Hence it is not reversible process.
b) Nichrome wire is made of alloys and has high resistance. When current is passed through it, heat is produced. So, here electrical energy is converted into heat energy. Hence, it is not a
reversible process.
(c) It is the process by which heat is transmitted from one point to another through a substance in the direction of fall of temperature without the actual movement of the particles of the substances themselves. Hence, it cannot be reversible.
d) Isothermal compression is reversible, for example-Carnot cycle, Heat engine. Thus, choice (d) is correct.
The temperature of inversion of a thermocouple is 620°C and the neutral temperature is 300oC, what is the temperature of cold junction?
20o C
320o C
-20o C
40o C
An ideal gas heat engine operates in Carnot cycle between 227o C and 127o C. It absorbs 6 × 104 cal of heat at higher temperature. Amount of heat converted to work is
2.4 × 104 cal
6 × 104 cal
1.2 × 104
4.8 × 104 cal
Two vibrating tuning forks produce progressive waves given by y1 = 4 sin 500 πt and y2 = 2 sin 506 Πt. Number of beats produced per minute is
360
180
3
60
The displacement x of a particle varies with time t as, where a, b α and β are positive constants. The velocity of the particle will
go on decreasing with time
be independent of
drop to zero when
go on increasing with time
A coil in the shape of an equilateral triangle of side l is suspended between the pole pieces of a permanent magnet such that B is in plane of the coil. If due to current i in the triangle a torque T acts on it, the side l of the triangle is
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