A 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 = 2r_o, l = 2l_o

• r = 2r_o, l = l_o

• r = r_o, l = l_o

• r = r_o, l = l_o

13.

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

The temperature of inversion of a thermocouple is 620°C and the neutral temperature is 300^oC, what is the temperature of cold junction?

• 20^o C

• 320^o C

• -20^o C

• 40^o C

An ideal gas heat engine operates in Carnot cycle between 227^o C and 127^o 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, $\mathrm{x} = {\mathrm{ae}}^{-\mathrm{\alpha t}} +\mathrm{b} {\mathrm{e}}^{ \mathrm{\beta t}}$ where a, b α and β are positive constants. The velocity of the particle will

• go on decreasing with time

• be independent of $\mathrm{\alpha } \mathrm{and} \mathrm{\beta }$

• drop to zero when $\mathrm{\alpha } = \mathrm{\beta }$

• 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