$\mathrm{y} = 3 \sin \mathrm{\pi }\mathrm{ }\left(\frac{\mathrm{t}}{2} - \frac{\mathrm{x}}{4}\right)$ represents an equation of a progressive wave, where t is in second and x is in metre. The distance travelled by the wave in 5 s is

• 8 m

• 10 m

• 5 m

• 32 m

A cylindrical tube open at both the ends has a fundamental frequency of 390 Hz in air. If $\frac{1}{4}$th of the tube is immersed vertically in water the fundamental frequency of air column is

• 260 Hz

• 130 Hz

• 390 Hz

• 520 Hz

23.

The surface temperature of the stars is determined using

• Planck's law

• Wien's displacement law

• Rayleigh-Jeans law

• Kirchhoff's law

Horizontal tube of non-uniform corss-section has radii of 0.1 m and 0.05 m respectively at M and N. For a streamline flow ofl iquid the rate of liquid flow is

• changing continuously with time

• greater at M than at N

• greater at N than at M

• same at M and N

A direct current I flows along the length of an infinitely long straight thin walled pipe, then the magnetic field is

• uniform throughout the pipe but not zero

• zero only along the axis of the pipe

• zero at any point inside the pipe

• maximum at the centre and minimum at the edge

Three resistors 1 Ω, 2 Ω and 3 Ω are connected to form a triangle. Across 3 Ω res1stor a 3 V battery is connected. The current through 3 Ω resistor is

• 0.75 A

• 1 A

• 2 A

• 1.5 A

Ferromagnetic materials used in a transformer must have

• low permeability and high hysterisis loss

• high permeability and low hysterisis loss

• high permeability and high hysterisis loss

• low permeability and low hysterisis loss

The accurate measurement of emf can be obtained using

• multimeter

• voltmeter

• voltameter

• potentiometer

An electric heater rated 220 V and 550 W is connected to AC mains. The current drawn by it is

• 0.8 A

• 2.5 A

• 0.4 A

• 1.25 A

In fog, photographs of the objects taken with infrared radiations are more clear than those obtained during visible light because

• I-R radiation has lesser wavelength than visible radiation

• scattering of I-R light is more than visible light

• the intensity of I-R light from the object is less

• scattering of I-R light is less than visible light