Alternating Current — Physics STD 12 Science — Question

Lamps used for household lighting are connected in

(a) Series

(b) Parallel

(c) Mixed circuit

(d) None of the above

A square metallic wire loop of side 0.1 m and resistance of 1W is moved with a constant velocity in a magnetic field of 2 wb/m² as shown in figure. The magnetic field is perpendicular to the plane of the loop, loop is connected to a network of resistances. What should be the velocity of loop so as to have a steady current of 1mA in loop

(a) 1 cm/sec

(b) 2 cm/sec

(c) 3 cm/sec

(d) 4 cm/sec

Equivalent capacitance between A and B is

(a) 8 μC

(b) 6 μF

(c) 26 μF

(d) 10/3 μF

Two resistors R and 2R are connected in series in an electric circuit. The thermal energy developed in R and 2R are in the ratio:

1. 1 : 2.
2. 2 : 1.
3. 1 : 4.
4. 4 : 1.

In a charged capacitor, the energy resides:

Two or more resistors are said to be in ...A... if one end of all resistors is joined together and similarly the other ends joined together, Here, A refers to:

Nucleus produced due to a-decay of the nucleus   is

(a)

(b)

(c)

(d)

The time period of a vibration magnetometer is T₀. Its magnet is replaced by another magnet whose moment of inertia is 3 times and magnetic moment is 1/3 of the initial magnet. The time period now will be

(a) 3T0

(b) T0

(c)

(d) T0/3

In a p-type semiconductor, the acceptor valence band is:

Free ²³⁸U nuclei kept in a train emit alpha particles. When the train is stationary and a uranium nucleus decays, a passenger measures that the separation between the alpha particle and the recoiling nucleus becomes x in time t after the decay. If a decay takes place when the train is moving at a uniform speed v, the distance between the alpha particle and the recoiling nucleus at a time t after the decay, as measured by the passenger will be:

1. x + vt
2. x - vt
3. x
4. depends on the direction of the train.