Current Electricity — Physics STD 12 Science — Question

What will be the equivalent resistance between the two points A and D

(a) 10 Ω

(b) 20 Ω

(c) 30 Ω

(d) 40 Ω

Two free parallel wires carrying currents in opposite direction

(a) Attract each other

(b) Repel each other

(c) Neither attract nor repel

(d) Get rotated to be perpendicular to each other

Light energy emitted by stars is due to

(a) Breaking of nuclei	(b) Joining of nuclei
(c) Burning of nuclei	(d) Reflection of solar light

A sinusoidal voltage of peak value 200 volt is connected to a diode and resistor R in the circuit shown so that half wave rectification occurs. If the forward resistance of the diode is negligible compared to R the rms voltage (in volt) across R is approximately

(a) 200

(b) 100

(c)

(d) 280

Assertion  :   Silicon is preferred over germanium for making semiconductor devices.

Reason      : The energy gap for germanium is more than the energy gap of silicon.

(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.

When npn transistor is used as an amplifier:

The avalanche breakdown in p-n junction is due to:

If a glass prism is dipped in water, its dispersive power:

1. Increases.
2. Decreases.
3. Does not change.
4. May increase or decrease depending on whether the angle of the prism is less than or greater than 60°.

In given figure, the potentiometer wire AB has a resistance of 5 W and length 10 m. The balancing length AM for the emf of 0.4 V is

(a) 0.4 m

(b) 4 m

(c) 0.8 m

(d) 8 m