Current Electricity — Physics STD 12 Science — Question

As shown in the figure, a very thin sheet of aluminium is placed in between the plates of the condenser. Then the capacity

(a) Will increase	(b) Will decrease
(c) Remains unchanged	(d) May increase or decrease

Biological importance of Ozone layer is 

(a) It stops ultraviolet rays

(b) Ozone rays reduce green house effect

(c) Ozone layer reflects radio waves

(d) Ozone layer controls   radio in atmosphere

When the current change from + 2A to – 2A in 0.05 second, an e.m.f. of 8 V is induced in a coil. The coefficient of self-induction of the coil is

(a) 0.1 H

(b) 0.2 H

(c) 0.4 H

(d) 0.8 H

Brilliance of diamond is due to

(a) Shape	(b) Cutting
(c) Reflection	(d) Total internal reflection

In order to pass 10% of main current through a moving coil galvanometer of 99 ohm, the resistance of the required shunt is

(a) 9.9 Ω

(b) 10 Ω

(c) 11 Ω

(d) 9 Ω

In a PNP transistor working as a common-base amplifier, current gain is 0.96 and emitter current is 7.2 mA. The base current is

(a) 0.4 mA

(b) 0.2 mA

(c) 0.29 mA

(d) 0.35 mA

In the circuit shown here  and battery B = 20V. The switch  is first closed. It is then opened and afterwards   is closed. What is the charge finally on

(a) 120 μC

(b) 80 μC

(c) 40 μC

(d) 20 μC

In Boolean algebra, Y = A + B implies that:

When stopping potential is applied in an experiment on photoelectric effect, no photocurrent is observed. This means that:

1. The emission of photoelectrons is stopped.
2. The photoelectrons are emitted but are reabsorbed by the emitter metal.
3. The photoelectrons are accumulated near the collector plate.
4. The photoelectrons are dispersed from the sides of the apparatus.