Physics

Hole is
(a) An anti-particle of electron
(b) A vacancy created when an electron leaves a covalent bond
(c) Absence of free electrons
(d) An artificially created particle

A 220 V AC supply is connected between points A and B (figure). What will be the potential difference V across the capacitor?

In figure given on next page, assuming the diodes to be ideal
(a) D₁is forward biased and D₂ is reverse biased and hence current flows from A to B
(b) D₂ is forward biased and D₁ is reverse biased and hence no current flows from B to A and vice-versa
(c) D₁ and D₂ are both forward biased and hence current flows from A to B
(d) D₁ and D₂ are both reverse biased and hence no current flows from A to B and vice-versa

In figure given below V₀ is the potential barrier across a pn junction when no battery is connected across the junction

(a) 1 and 3 corresponds to forward bias of junction

(b) 3 corresponds to forward bias of junction and 1 corresponds to reverse bias of the junction

(c) 1 corresponds to forward bias and 3 corresponds to reverse bias of the junction

(d) 3 and 1 both corresponds to reverse bias of the junction

The conductivity of a semiconductor increases with increase in temperature, because
(a) Number density of free current carries increases
(b) Relaxation time increases
(c) Both number density of carries and relaxation time increase
(d) Number density of carries increases, relaxation time decreases but effect of decrease in relaxation time is much less than increase in number density 

A Zener of power rating 1 W is to be used as a voltage regulator. If Zener has a breakdown of 5 V and it has to regulate voltage which fluctuated between 3 V and 7 V, what should be the value of Rs for safe operation (see figure)?

Write the truth table for the circuit shown in figure given below. Name the gate that the circuit resembles.

Explain why elemental semiconductor cannot be used to make visible LEDs.

How would you set up a circuit to obtain NOT gate using a transistor?

Two car garages have a common gate which needs to open automatically when a car enters either of the garages or cars enter both. Draw a circuit that resembles this situation using diodes for this situation.