Two bodies A and B, have thermal emissivities of 0.01 and 0.81 respectively. The outer surface areas of both the bodies are same and emit the same radiated power. The wavelength λB , corresponding to the maximum intensity in radiation from B, is shifted from the wavelength λA , corresponding to the maximum intensity in radiation from A, by 1 µm. If the temperature of A is 5802 k, then the temperature and wavelength λB of body B are
1934 K, 3.5 µm
1934 K, 1.5 µm
1728 K, 32 µm
1764 K, 1.8 µm
The equation of a simple harmonic wave is given by y = 3sin (50 t - x) where, x and y are in meters and t in seconds. The ratio of maximum particle velocity to the wave velocity is
2
Two strings with mass per unit length of 9 gcm-1 and 25 gcm-1 are joined together in series. The reflection coefficient for the vibration waves are
An ideal heat engine exhausting heat at 27° C is to have 25% efficiency. It must take heat at
127 °C
227° C
327° C
None of these
A.
127 °C
A magnet is made to oscillate with a particular frequency, passing through a coil as shown in the figure. The time variation of the magnitude of emf generated across the coil during one cycle is
Two spherical soap bubbles of radii r1 and r2 in vacuum combine under isothermal conditions. The resulting bubble has a radius equal to
A wooden block is floating on water kept in a beaker, 40% of the block is above the water surface. Now the beaker is kept inside a lift that starts going upward with acceleration equal to . The block will then
sink
float with 10% above the water surface
float with 40% above the water surface
float with 70% above the water surface
A bar magnet has a coercivity of 4 x 103 Am-1. It is placed inside a solenoid of length 12 cm having 60 turns in order to demagnetise it. The amount of current that should be passed through the solenoid is
16 A
8 A
4 A
2 A
A series R-L-C circuit driven with Erms = 100V and frequency fd = 50 Hz is shown below.
What new capacitance should be connected to maximize the average power, if other parameters of the circuit are not changed ?
41.6 µF
33.5 µF
39.8 µF
31.3 µF
A bar magnet of length l and magnetic dipole moment M is bent in the form of an arc as shown in figure. The new magnetic dipole moment will be
M