Reverse Bias

Q.

Determine the current in each branch of the network shown in fig 3.30:

Q. Calculate the amount of charge on capacitor of $4\mu F$. The internal resistance of battery is $1\Omega$ :

1. $16\mu C$
2. $8\mu C$
3. $\text{zero}$
4. $4\mu C$

Q. What is a meaning of bias or biasing?

Q. If a small sphere of mass m and charge q is hung from a silk thread at an angle theta with the surface of a vertical charged conducting plate; then for equilibrium of sphere the surface charge density of the plate

Q.

In which region transistor acts as a switch?

Q. The $\text{I - V}$ characteristics of a $\text{p-n}$ junction diode in forward bias is shown in the figure. The ratio of the dynamic resistance, corresponding to forward biast voltage of $2V\text{and}4V$ respectively, is

1. $1:2$
2. $1:40$
3. $20:1$
4. $5:1$

Q. A transistor is connected in common-emitter (C-E) configuration. The collector supply is 8V and the voltage drop across a resistor of 800 $\Omega$ in the collector circuit is 0.5V. If the current gain factor $\left(\alpha \right)$ is 0.96, find the base current.

1. $28\mu A$
2. $24\mu A$
3. $25\mu A$
4. $26\mu A$

Q. The equivalent resistance of the circuit across $AB$ is given by (the diodes are ideal)

1. $6\Omega$ or $9\Omega$
2. $4\Omega$ or $9\Omega$
3. $4\Omega$ or $13\Omega$
4. $6\Omega$ or $0\Omega$

Q. (a) Draw the circuit diagram for studying the characteristics of a transistor in common emitter configuration. Explain briefly and show how input and output characteristics are drawn.
(b) The figure shows input waveforms A and B to a logic gate. Draw the output waveform for an OR gate. Write the truth table for this logic gate and draw its logic symbol.

Q.

What happens when a diode is shorted?

Q.

The part of a transistor that is heavily doped to produce a large number of majority carriers is

1. Base

2. Emitter

3. Collector

4. None of these

Q. A small conducting sphere of radius r is lying concentrically inside a bigger hollow Conducting of radius R. The bigger and smaller spheres are charge with Q and q (Q>q) and are insulated from each other. The potential difference between the spheres will be

Q. For a closed surface the flux associated is is 5 ifadding -75uc to it it becomes 2 initial charge enclosed by the surface will be a)125uc b) -20uc

Q. The reverse biasing in a PN junction diode

1. decreases the potential barrier
2. increases the potential barrier
3. increases the number of majority charge carriers
4. increases the number of minority charge carriers

Q.
In the circuit shown, the value of $\beta$ of the transistor is 48. If the base current supplied $200\mu A$, what is the voltage at the terminal Y?

1. 0.2 V
2. 0.5 V
3. 4 V
4. 4.8 V

Q.

What is the current in the circuit shown below

1. 0 amp

2. 1 amp

3. 0.10 amp

4. 
   

Q.

Draw V-I characteristics of a p-n junction diode. Answer the following questions, giving reasons :
(i) Why is the current under reverse bias almost independent of the applied potential upto a critical voltage?
(ii) Why does the reverse current show a sudden increase at the critical voltage?
Name any semiconductor device which operates under the reverse bias in the breakdown region.

Q.

When a PN junction diode is reverse biased

1. Height of the potential barrier decreases

2. No change in the current takes place

3. Electrons and holes are attracted towards each other and move towards the depletion region

4. Electrons and holes move away from the junction depletion region

Q.
When a DC voltage is applied at the two ends of a circuit kept in a closed box, it is observed that the current gradually increases from zero to a certain value and then remains constant. What do you think that the circuit contains?

1. A resistor alone
2. A capacitor alone
3. A resistor and a inductor in series
4. A resistor and a capacitor in series

Q. In an AC circuit, the power factor

1. is unity when the circuit contains an ideal resistor only.
2. is zero when the circuit contains an ideal inductor only.
3. Both options $\left(A\right)$ and $\left(B\right)$
4. None of these

Q.

What is transistor gain?

Q. In a PN-junction diode,

1. the current in the reverse biased condition is generally very small
2. the current in the reverse biased condition is small but the forward biased current is independent of the bias voltage
3. the reverse biased current is strongly dependent on the applied bias voltage
4. the forward biased current is very small in comparison to reverse biased current

Q. Two capacitors of capacitances C and 2C are charged to potentials 2V and V respectively and then these capacitors are disconnected from the charging batteries. Now capacitors are connected together such that their opposite polarity plates are connected together. The loss in potentialenergy of the system, is

1. $\frac{3}{8}C{V}^2$
2. $\frac{3}{2}C{V}^2$
3. $\frac{3}{4}C{V}^2$
4. $3C{V}^2$

Q.

What is forward and reverse bias?

Q. if the dis†an ce between two charges is incresed by 20% than its firce will be ?

Q.

When the diode is forward biased it is equal to?

Q. Consider the situation shown in figure. The switch $S$ is open for a long time and then closed. Find the charge flown through the battery when the switch is closed.

1. $CE/2$
2. $CE$
3. $CE/4$
4. $0$

Q. A conductor initially free from charge is charged by repeated contacts with a plate which after each contact is replenished to a charge $Q$. If $q$ is the charge on the conductor after first operation, then the maximum charge which can be given to the conductor in this way will be:
(When 2 conductors are in contact, potential on them becomes equal)

1. $\frac{3Qq}{2Q+q}$
2. $\frac{2Qq}{Q+q}$
3. $\frac{Qq}{Q+q}$
4. $\frac{Qq}{Q-q}$

Q.

How do transistors amplify signals?

Q. In the circuit given below, neglecting base emitter voltage $V_{BE}$, find the collector current.

1. $0.78mA$
2. $0.96mA$
3. $1.28mA$
4. $2.20mA$