Physics Test 20...

Photons of energy 1eV and 2.5 eV successively illuminate a metal whose work function is 0. 5 eV. The ratio of the maximum speeds of the electrons emitted will be

When a charged oil drop moves upwards in an electric field, the electric force acting on the drop is

The material which practically does not show elastic after effect is

The average power dissipation in a pure capacitor in AC circuit is

A boat crosses a river from port A to port B, which are just on the opposite side. The speed of the water is vW and that of boat is vB relative to water. Assume vB = 2vW. What is the time taken by the boat, if it has to cross the river directly on the AB line?

The root mean square velocity of the molecules in a sample of helium is 5/7th that of the moelcules in a sample of hydrogen. If the temperature of hydrogen sample is 0^oC, then the temperature of the helium sample is about

The electric potential at a point (x, y) in the xy-plane is given by: V = -kxy. The electric field intensity at a distance r from the origin varies as

A student has measured the length of a wire equal to 0.04580 m. This value of length has the number of significant figures equal to

The capacity of a parallel plate condenser is 10 μ Fd without dielectric. After that, a dielectric of constant 2 is used to fill half thickness between the plates of another capacitor of same capacitance. The net capacitance after joining both of them in series in μ Fd is

If the earth is at one-fourth of its present distance from the sun, then duration of the year will be