Electromagnetic Waves — Physics STD 12 Science — Question

The magnetic field energy in an inductor changes from maximum value to minimum value in 5.0ms when connected to an AC source. The frequency of the source:

Two metal spheres of radii  and  are charged to the same potential. The ratio of charges on the spheres is

(a)

(b)

(c)

(d)

Diameter of a plano–convex lens is 6 cm and thickness at the centre is 3 mm. If the speed of light in the material of the lens is 2 × 10⁸ m/sec, the focal length of the lens is

(a) 15 cm

(b) 20 cm

(c) 30 cm

(d) 10 cm

For the same speed, de Broglie wavelength.

Assertion :   The capacity of a given conductor remains same even if charge is varied on it.

Reason      : Capacitance depends upon nearly medium as well as size and shape of conductor.

(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.

(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.

(c) If assertion is true but reason is false.

(d) If the assertion and reason both are false.

In a cyclotron, a charged particle:

A copper voltameter is connected in series with a heater coil of resistance 0.1 Ω. A steady current flows in the circuit for twenty minutes and mass of 0.99 g of copper is deposited at the cathode. If electrochemical equivalent of copper is 0.00033 gm/C, then heat generated in the coil is

(a) 750 J

(b) 650 J

(c) 350 J

(d) 250 J

A two metre wire is moving with a velocity of 1 m/sec perpendicular to a magnetic field of 0.5 weber/m². The e.m.f. induced in it will be

(a) 0.5 volt

(b) 0.1 volt

(c) 1 volt

(d) 2 volt

A magnetic field cannot exert any force on a: