Electromagnetic Induction — Physics STD 12 Science — Question

The distance between the circular plates of a parallel plate condenser 40mm  in diameter,  in order to have same capacity as a sphere of radius 1 metre is

(a) 0.01 mm

(b) 0.1 mm

(c) 1.0 mm

(d) 10  mm

The work function of a photoelectric material is 3.3 eV. The threshold frequency will be equal to

(a) 8

(b) 8

(c) 8

(d) 8

When a negative charge is taken at a height from earth's surface, then its potential energy   

(a) Decreases	(b) Increases
(c) Remains unchanged	(d) Will become infinity

If the number of turns in a moving coil galvanometer is increased its sensitivity :

The reading of a high resistance voltmeter when a cell is connected across it is 2.2 V. When the terminals of the cell are also connected to a resistance of 5Ω the voltmeter reading drops to 1.8 V. Find the internal resistance of the cell

(a) 1.2 Ω

(b) 1.3 Ω

(c) 1.1 Ω

(d) 1.4 Ω

For the transistor circuit shown below, if b = 100, voltage drop between emitter and base is 0.7 V then value of V_CE will be

(a) 10 V

(b) 5 V

(c) 13 V

(d) 0 V

Assertion   :  Electric appliances with metallic body have three connections, whereas an electric bulb has a two pin connection.

Reason       : Three pin connections reduce heating of connecting wires.

(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.

What do you understand by the static or frictional electricity?

A point charge of 40 stat coulomb is placed 2 cm in front of an earthed metallic plane plate of large size. Then the force of attraction on the point charge is

(a) 100 dynes

(b) 160 dynes

(c) 1600 dynes

(d) 400 dynes