Zener Diode

Q. In the given circuit, the current through Zener diode is $\frac{5k}{3}\text{mA}$. The value of $k$ is

1. $1$
2. $3$
3. $2$
4. $6$

Q. For the circuit shown below, the current through the Zener diode is

1. $9\text{mA}$
2. $5\text{mA}$
3. Zero
4. $14\text{mA}$

Q. A Zener diode, having breakdown voltage equal to $15V$, is used in a voltage regulator circuit shown in figure. The current through the diode is:

1. $5mA$
2. $15mA$
3. $10mA$
4. $20mA$

Q.

Why does the depletion layer increase in reverse biasing?

Q.

Zener breakdown occurs in a p-n junction having p and n both

1. lightly doped and have a wide depletion layer

2. heavily doped and have a narrow depletion layer

3. heavily doped and have a wide depletion layer

4. lightly doped and have a narrow depletion layer

Q. The instantaneous values of alternating current and voltages in a circuit are given as
$I=\frac{1}{\sqrt{2}}\sin \left(100\pi t\right)\text{A}$
$V=\frac{1}{\sqrt{2}}\sin (100\pi t+\frac{\pi }{3})\text{V}$
The average power (in watts) consumed in the circuit is

1. $\frac{1}{2}$
2. $\frac{1}{8}$
3. $\frac{1}{4}$
4. $\frac{\sqrt{3}}{4}$

Q. For the circuit shown, find current through the Zener diode.

1. 0.3 mA
2. 0.5 mA
3. 0.4 mA
4. 0.6 mA

Q. In the given circuit, the current through the zener diode is:

1. 0 mA
2. 3.33 mA
3. 6.67 mA
4. 10 mA

Q. In a parallel plate capacitor, each plate having an area $6\times {10}^{-3}{m}^2$ and distance between the plates $3\text{mm}$ is connected to a 100 V supply. If a $3\text{mm}$ thick mica sheet (of dielectric constant = 6) is inserted between the plates, calculate the capacitance and charge on each plate
A) While the voltage supply remained connected

In a parallel plate capacitor, each plate having an area $6\times {10}^{-3}{m}^2$ and distance between the plates $3\text{mm}$ is connected to a 100 V supply. If a $3\text{mm}$ thick mica sheet (of dielectric constant = 6) is inserted between the plates, calculate the capacitance and charge on each plate
B) after the supply was disconnected

Q. All bulbs in the circuit shown in the figure are identical. Which bulb has maximum brightness .

1. $\text{B}$
2. $\text{A}$
3. $\text{D}$
4. $\text{C}$

Q.

Why is Zener diode heavily doped?

Q.

Name the instrument used to measure the potential difference.

Q. Why is the electric field of a junction in zener diode very high when the depletion region is very thin ??? Pls give a theoretical explanation.

Q. The reverse breakdown voltage of a Zener diode is $5.6V$ in the given circuit.
The current $I_Z$ through the Zener is

1. $7mA$
2. $17mA$
3. $10mA$
4. $15mA$

Q. IF R1 and R2 are the resistance of 2 resistors having 50W and 100W respectively designed to operate at same voltage then R1 by R2

Q. What is realisation of logic gates?????

Q. In the given circuit diagram, find the heat generated on closing the switch $S$. (Initially the capacitor of capacitance $C$ is uncharged)

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

Q. Identify the logic operation carried out by the given circuit:
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Q. Three capacitors $C_1,C_2$ and $C_3$ are connected to a battery as shown in the figure. The three capacitors have equal capacitances. Which capacitor stores the most energy?

1. $C_1$ or $C_3$as they store the same amount of energy
2. All three capacitors store the same amount of energy
3. $C_1$
4. $C_2$

Q. The combination of logic gates shown in circuit is given input $A=0$ and $B=1$.


The output at $Y$ will be

1. $0$
2. $1$
3. $1$ always irrespective of the inputs
4. $0$ always irrespective of the inputs

Q. The output of an OR gate is connected to both the inputs of a NAND gate, the combination will serve as a

1. OR gate
2. AND gate
3. NOR gate
4. NOT gate

Q. For the following logic gates circuit, what is the correct expression for its output?

1. $X=(B.A)+B$
2. $X=B+\overline{(A+B)}$
3. $X=B+\left(\overline{A\cdot B}\right)$
4. $X=B+(A\cdot \overline{B})$

Q.

A transformer is used to light 100 W – 110 V lamp from 220 V mains. If the main current is 0.5 A, the efficiency of the transformer is

1. 96$\%$

2. 90 $\%$

3. 99 $\%$

4. 95 $\%$

Q. Three similar light bulbs are connected to a constant voltage d.c. supply as shown in the figure. Each bulb operates at normal brightness and the ammeter (of negligible resistance) registers a steady current.

The filament of one of the bulbs breaks. What happens to the ammeter reading and to the brightness of the remaining bulbs ?

1. Both ammeter reading and bulb brightness increases.
2. Ammeter reading increases and bulb brightness remains unchanged.
3. Both ammeter reading and bulb brightness remains unchaanged.
4. Ammeter reading decreases and bulb brightness remains unchanged.

Q. A battery having emf $E_1=100\text{V}$ and internal resistance $r=0.5\Omega$ is connected to a storage battery of emf $E_2=90\text{V}$ and external resistance $R$ as shown in figure. For what value of $R$ no current will pass through storage battery $E_2$?

1. $2.5\Omega$
2. $4.5\Omega$
3. $5.5\Omega$
4. $7.5\Omega$

Q. Both the diodes used in the circuit shown are assumed to be ideal and have negligible resistance, when these are forward biased. Built-in potential in each diode is $0.7\text{V}$. For the input voltages shown in the figure, the voltage (in Volts) at point $A$ is .

Q. From the zener diode circuit shown in figure, the current through the zener diode is:

1. 34 mA
2. 31.5 mA
3. 2.5 mA
4. 36.5 mA

Q. (1)Answer the following question: In any ac circuit, is the applied instantaneous voltage equal to the algebraic sum of the instantaneous voltages across the series elements of the circuit? Is the same true for rms voltage?

$2)$Answer the following question: A capacitor is used in the primary circuit of an induction coil. Why?

$3)$ Answer the following question:
An applied voltage signal consists of a superposition of a dc voltage and an ac voltage of high frequency. The circuit consists of an inductor and a capacitor in series. Show that the dc signal will appear across $C$ and the ac signal across$L.$

$4)$ Answer the following question: A choke coil in series with a lamp is connected to a dc line. The lamp is seen to shine brightly. Insertion of an iron core in the choke causes no change in the lamp’s brightness. Predict the corresponding observations if the connection is to an ac line.

$5)$Answer the following question: Why is choke coil needed in the use of fluorescent tubes with ac mains? Why can we not use an ordinary resistor instead of the choke coil?

Q. An apparatus is connected to an ideal battery as shown in figure. For what value of current, power delivered to the apparatus will be maximum?

1. $\frac{E}{4R}$
2. $\frac{E}{2R}$
3. information insufficient
4. $\frac{E}{R}$++

Q. If $E=6\text{V}$, $r=2R$ then maximum power dissipated through $R$ is

1. $18\text{W}$
2. $9\text{W}$
3. $36\text{W}$
4. $3\text{W}$