Current Electricity — Physics STD 12 Science — Question

When the P end of P-N junction is connected to the negative terminal of the battery and the N end to the positive terminal of the battery, then the P-N junction behaves like          

(a) A conductor

(b) An insulator

(c) A super-conductor

(d) A semi-conductor

The total charge induced in a conducting loop when it is moved in magnetic field depends on

(a) The rate of change of magnetic flux	(b) Initial magnetic flux only
(c) The total change in magnetic flux	(d) Final magnetic flux only

Radioactivity is

(a) Irreversible process	(b) Self disintegration process
(c) Spontaneous process	(d) All of the above

There is 10 units of charge at the centre of a circle of radius 10m. The work done in moving 1 unit of charge around the circle once is

(a) Zero

(b) 10 units

(c) 100 units

(d) 1 unit

Assertion  :   Current is passed through a metallic wire, heating it red. When cold water is poured on half of its portion, then rest of the half portion become more hot.  

Reason    : Resistances decreases due to decrease in temperature and so current through wire increases.

(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.

Consider the process on a system shown in figure. During the process, the work done by the system:

1. Continuously increases.
2. Continuously decreases.
3. First increases then decreases.
4. First decreases then increases.

Assertion  :  A transistor amplifier in common emitter configuration has a low input impedence.

Reason      : The base to emitter region is forward biased.

(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.

The magnitude of gravitational potential energy of the moon-earth system is U with zero potential energy at infinite separation. The kinetic energy of the moon with respect to the earth is K.

1. U < K
2. U > K
3. U = K

The following configuration of gate is equivalent to

(a) NAND

(b) XOR

(c) OR

(d) None of these

The value of plate current in the given circuit diagram will be

(a) 3 mA

(b) 8 mA

(c) 13 mA

(d) 18 mA