Electronic Devices | Physics JEE previous year questions with Solutions

Q 1 :

Conductivity of a photodiode starts changing only if the wavelength of incident light is less than 660 nm. The band gap of photodiode is found to be $(\frac{x}{8}) e V$ . The value of X is (Given, $h = 6.6 \times 10^{- 34} J s, e = 1.6 \times 10^{- 19} C$ ) [2024]

15
11
13
21

1

2

3

4

(1)

$Energy bond gap E_{g} is$

$E_{g} = \frac{h c}{λ} = \frac{1240}{λ (in nm)}$

$= \frac{1240}{660} = 1.87 eV$

$or E_{g} = (\frac{15}{8}) eV$

$∴ x = 15$

Q 2 :

The value of net resistance of the network as shown in the given figure is [2024]

$(5 / 2) Ω$
$(30 / 11) Ω$
$(15 / 4) Ω$
$6 Ω$

1

2

3

4

(4)

Diode 2 is in reverse bias, so current will not flow in branch of 2nd diode, So we can assume it to be broken wire.
Diode 1 is in forward bias, so it will behave like conducting wire. The circuit is equivalent to

$R_{e q} = \frac{15 \times 10}{15 + 10} = \frac{15 \times 10}{25} = 6 Ω$

Q 3 :

Which of the diode circuit shows correct biasing used for the measurement of dynamic resistance of p-n junction diode? [2024]

1

2

3

4

(2)

For conduction of current, diode must be in forward biased mode.
So, option (2) is correct.

Q 4 :

The I-V characteristics of an electronic device shown in the figure. The device is: [2024]

a solar cell
a transistor which can be used as an amplifier
a Zener diode which can be used as a voltage regulator
a diode which can be used as a rectifier

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(3)

It is a theoretical conceptual question. Zener diode used as voltage regulator

Q 5 :

Which of the following circuits is reverse-biased? [2024]

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4

(4)

Q 6 :

In the given circuit, the breakdown voltage of the Zener diode is 3.0 V. What is the value of $I_{Z}$ ? [2024]

3.3 mA
5.5 mA
10 mA
7 mA

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3

4

(2)

Breakdown voltage of the Zener diode, $V_{z} = 3 V$

Let potential at $B = 0 V$

Potential at $E (V_{P}) = 10 V$ and $V_{C} = V_{A} = 3 V$

$I = \frac{10 - 3}{1000} = \frac{7}{1000} A and I_{1} = \frac{3}{2000} A$

Also, $I_{Z} + I_{1} = I$

Therefore, $I_{Z} = \frac{7 - 1.5}{1000} = 5.5 mA$

Q 7 :

A Zener diode of breakdown voltage 10V is used as a voltage regulator as shown in the figure. The current through the Zener diode is [2024]

50 mA
0
30 mA
20 mA

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(3)

$i_{1} = \frac{20 - 10}{200} = \frac{1}{20}$

$i_{2} = \frac{10 - 0}{500} = \frac{1}{50}$

$i_{z} = i_{1} - i_{2} = \frac{1}{20} - \frac{1}{50}$

$= \frac{3}{100} A = 30 mA$

Q 8 :

In the given circuit, the voltage across load resistance $(R_{L})$ is [2024]

8.75 V
9.00 V
8.50 V
14.00 V

1

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4

(1)

${(V_{B})}_{S i} = 0.7 V$

${(V_{B})}_{G e} = 0.3 V$

Voltage drop across both diodes $= 0.7 + 0.3 = 1 V$

So remaining 14 volts will drop across $R_{L} \Rightarrow$

$V_{L} = \frac{2.5}{(1.5 + 2.5)} \times 14 = \frac{2.5}{4} \times 14 volt = 8.75 volt$

Q 9 :

In the given circuit if the power rating of Zener diode is 10 mW, the value of series resistance $R_{s}$ to regulate the input unregulated supply is [2024]

0.5 $kΩ$
10 $Ω$
1 $kΩ$
10 $kΩ$

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4

(1)

Potential difference across $R_{s}$

$V_{1} = 8 - 5 = 3 V$

Current through the load resistor

$I = \frac{5}{1 \times 10^{3}} = 5 mA$

Maximum current through Zener diode

$I_{z max.} = \frac{10}{5} = 2 mA$

and minimum current through Zener diode

$I_{z min.} = 0$

$∴$ $I_{s max.} = 5 + 2 = 7 mA$

and $R_{s min} = \frac{V_{1}}{I_{s max.}} = \frac{3}{7} k Ω$

Similarly, $I_{s min.} = 5 mA$

and $R_{s max.} = \frac{V_{1}}{I_{s min.}} = \frac{3}{5} k Ω$

$∴$ $\frac{3}{7} k Ω < R_{s} < \frac{3}{5} k Ω$

Q 10 :

A potential divider circuit is connected with a DC source of 20 V, a light-emitting diode of glow in voltage 1.8 V and a Zener diode of breakdown voltage of 3.2 V. The length (PR) of the resistive wire is 20 cm. The minimum length of PQ to just glow the LED is ____ cm. [2024]

(5)

$V_{P Q} = 3.2 + 1.8 = 5 V$

$And, V_{P R} = 20 V (given)$

Now $\frac{20 V}{20 cm} \times ℓ = 5 V$

Q 11 :

Which of the following circuits represents a forward biased diode? [2025]

Choose the correct answer from the options given below:

(B), (D) and (E) only
(A) and (D) only
(B), (C) and (E) only
(C) and (E) only

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(3)

For forward bias potential of p side should be higher than $n$ side.

Q 12 :

Refer to the circuit diagram given in the figure, which of the following observations are correct?

A. Total resistance of circuit is 6 $Ω$ .

B. Current in Ammeter is 1 A.

C. Potential across AB is 4 Volts.

D. Potential across CD is 4 Volts.

E. Total resistance of the circuit is 8 $Ω$ .

Choose the correct answer from the options given below: [2025]

A, B and D only
A, C and D only
B, C and E only
A, B and C only

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(1)

$Current through ammeter = 1 A$

$R_{net} = 6 Ω$

$V_{A B} = 0.5 \times 4 = 2 volt$

$V_{C D} = 1 \times 4 = 4 volt$

$A, B and D are correct.$

Q 13 :

What is the current through the battery in the circuit shown below? [2025]

1.0 A
1.5 A
0.5 A
0.25 A

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(3)

$Both diodes are in forward bias therefore$

$hence R_{eq} = 10 Ω$

$i = \frac{V}{R} = \frac{5}{10} = \frac{1}{2} A$

Q 14 :

Consider the following statements:

A. The junction area of solar cell is made very narrow compared to a photo diode.
B. Solar cells are not connected with any external bias.
C. LED is made of lightly doped p–n junction.
D. Increase of forward current results in continuous increase of LED light intensity.
E. LEDs have to be connected in forward bias for emission of light.

Choose the correct answer from the options given below: [2025]

B, D, E only
A, C only
A, C, E only
B, E only

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(4)

LED is connected in forward bias and its intensity increases up to certain value of current and further there is no change as intensity saturates.

Also solar cells are not connected with any external bias. So ‘B’ is also correct.

Q 15 :

In the circuit shown here, assuming threshold voltage of diode is negligibly small, then voltage $V_{A B}$ is correctly represented by: [2025]

$V_{A B}$ would be zero at all times

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(4)

Due to the diode the current will be allowed only along B to A through the resistor. Hence $V_{A B}$ will have only negative values i.e., the following graph represents the output voltage $V_{A B}$ .

Q 16 :

A zener diode with 5 V zener voltage is used to regulate an unregulated dc voltage input of 25 V.

For a 400 $Ω$ resistor connected in series, the zener current is found to be 4 times load current. The load current $(I_{L})$ and load resistance $(R_{L})$ are: [2025]

$I_{L} = 20 mA; R_{L} = 250 Ω$
$I_{L} = 10 A; R_{L} = 0.5 Ω$
$I_{L} = 0.02 mA; R_{L} = 250 Ω$
$I_{L} = 10 mA; R_{L} = 500 Ω$

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(4)

$5 I_{L} = \frac{(25 - 5)}{400} = \frac{1}{20} = 50 mA$

$I_{L} = 10 mA$

$5 = I_{L} R_{L}$

$R_{L} = \frac{5}{I_{L}} = \frac{5}{10 \times 10^{- 3}} = 500 Ω$

Q 17 :

In the following circuit, the reading of the ammeter will be (Take Zener breakdown voltage = 4V) [2025]

24 mA
80 mA
10 mA
60 mA

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(3)

$V_{1} = \frac{400}{100 + 400} \times 12 V = \frac{4}{5} \times 12 = \frac{48}{5} V$

$Here, V_{1} > V_{2}$

So, Zener breakdown will be taking place.

$Hence, voltage across 400 Ω will be 4V$

$I = \frac{4}{400} A = \frac{1}{100} A = 10 mA$

Q 18 :

The output voltage in the following circuit is (Consider ideal diode case) [2025]

10 V
0 V
+ 5 V
- 5 V

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(2)

$Here D_{1} is reverse biased and D_{2} is forward biased. Therefore,$ $current flows through D_{2} and 5 V drop on resistor. So, V_{out} = 0$

Q 19 :

Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R [2023]

Assertion A: Photodiodes are preferably operated in reverse bias condition for light intensity measurement.

Reason R: The current in the forward bias is more than the current in the reverse bias for a p–n junction diode.

In the light of the above statements, choose the correct answer from the options given below:

A is true but R is false
Both A and R are true and R is the correct explanation of A
A is false but R is true
Both A and R are true but R is NOT the correct explanation of A

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(4)

Photodiodes are operated in reverse bias as fractional change in current due to light is more easy to detect in reverse bias.

Q 20 :

Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R) [2023]

Assertion (A): Photodiodes are used in forward bias usually for measuring the light intensity.

Reason (R): For a p--n junction diode, at applied voltage 'V' the current in the forward bias is more than the current in the reverse bias for $| V_{z} |$ $> \pm V \geq$ $| V_{0} |$ where $V_{0}$ is the threshold voltage and $V_{z}$ is the breakdown voltage.

In the light of the above statements, choose the correct answer from the options given below:

A is true but R is false
A is false but R is true
Both A and R are true but R is not the correct explanation of A
Both A and R are true and R is correct explanation of A

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(2)

Photodiodes are usually used in forward Bias.

Q 21 :

Which of the following statement is not correct in the case of light emitting diodes? [2023]

A. It is a heavily doped p–n junction.
B. It emits light only when it is forward biased.
C. It emits light only when it is reverse biased.
D. The energy of the light emitted is equal to or slightly less than the energy gap of the semiconductor used.

Choose the correct answer from the options given below:

C and D
A
C
B

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(3)

LED works in forward biasing and light energy maybe slightly less or equal to band gap.

Q 22 :

Choose the correct statement about Zener diode [2023]

It works as a voltage regulator in reverse bias and behaves like simple p–n junction diode in forward bias.
It works as a voltage regulator in both forward and reverse bias.
It works a voltage regulator only in forward bias.
It works as a voltage regulator in forward bias and behaves like simple p–n junction diode in reverse bias.

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(1)

Works as voltage regulator in reverse bias and as simple P-N junction in forward bias.

Q 23 :

Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R [2023]

Assertion A: Diffusion current in a p–n junction is greater than the drift current in magnitude if the junction is forward biased.

Reason R: Diffusion current in a p–n junction is from the n-side to the p-side if the junction is forward biased.

In the light of the above statements, choose the most appropriate answer from the options given below:

Both A and R are correct and R is the correct explanation of A
Both A and R are correct but R is NOT the correct explanation of A
A is correct but R is not correct
A is not correct but R is correct

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(3)

In forward biased condition, diffusion of majority charge carriers takes place from $p$ -side to $n$ -side which constitute the diffusion current.

Q 24 :

A zener diode of power rating 1.6 W is to be used as voltage regulator. If the zener diode has a breakdown of 8 V and it has to regulate voltage fluctuating between 3 V and 10 V. The value of resistance $R_{s}$ for safe operation of diode will be [2023]

$13.3 Ω$
$12 Ω$
$10 Ω$
$13 Ω$

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(3)

$V_{b} = 8 volt$

$V_{A} - V_{B} = 8 volt$

$Current through zener diode,$

$i = \frac{P}{V} = \frac{1.6 W}{8 V} = 0.2 A$

$V_{C} - V_{A} = 10 - 8 volt$

$R = \frac{V_{C} - V_{A}}{i} = \frac{2 V}{0.2 A} = 10 Ω$

[Note: A zener diode can regulate only if input voltage $\geq$ zener breakdown voltage. The range of input voltage should be 8 to 10V so that output voltage remains constant = 8V]

Q 25 :

If each diode has a forward bias resistance of $25 Ω$ in the below circuit,

Which of the following options is correct [2023]

$\frac{I_{3}}{I_{4}} = 1$
$\frac{I_{2}}{I_{3}} = 1$
$\frac{I_{1}}{I_{2}} = 1$
$\frac{I_{1}}{I_{2}} = 2$

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(4)

$R_{e q} = \frac{150 \times 150}{300} + 25 = 100 Ω$

$I_{1} = \frac{5}{10} = 0.05 A$

$I_{2} = I_{4} = \frac{0.05}{2} = 0.025 A$

$\frac{I_{1}}{I_{2}} = 2$

Q 26 :

The following diagram shows a Zener diode as a voltage regulator. The Zener diode is rated at $V_{Z} = 5 V$ and the desired current in the load is $5 mA$ . The unregulated voltage source can supply up to $25 V$ . Considering the Zener diode can withstand four times of the load current, the value of resistor $R_{s}$ (shown in circuit) should be ____ $Ω$ . [2026]

1000
100
4000
10

1

2

3

4

(1)

(Dropped)

Q 27 :

The charge stored by the capacitor C in the given circuit in the steady state is____________ $μ c .$ . [2026]

5
10
7.5
12.5

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3

4

(2)

$i = \frac{2.5}{5} = 0.5 A$

$V_{c} = 4 \times 0.5$

$V_{c} = 2 V$

$Charge$

$Q = C V_{c}$

$= 5 \times 2$

$= 10 μ C$

Q 28 :

Assuming in forward bias condition there is a voltage drop of 0.7 V across a silicon diode, the current through diode $D_{1}$ in the circuit is ______ mA.

(Assume all diodes in the given circuit are identical) [2026]

18.8
17.6
20.15
11.7

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4

(1)

$12 - 0.3 \times 10^{3} I - 0.7 = 0$

$\frac{11.3}{0.3 \times 10^{3}} = I$

$37.66 \times 10^{- 3} A = I$

$Current through diode D_{1}, I_{1} = \frac{I}{2}$

$I_{1} = 18.83 mA$

Topic Question Set

Q 1 :

Conductivity of a photodiode starts changing only if the wavelength of incident light is less than 660 nm. The band gap of photodiode is found to be $(\frac{x}{8}) e V$ . The value of X is (Given, $h = 6.6 \times 10^{- 34} J s, e = 1.6 \times 10^{- 19} C$ ) [2024]

Q 2 :

The value of net resistance of the network as shown in the given figure is [2024]

Q 3 :

Which of the diode circuit shows correct biasing used for the measurement of dynamic resistance of p-n junction diode? [2024]

Q 4 :

The I-V characteristics of an electronic device shown in the figure. The device is: [2024]

Q 5 :

Which of the following circuits is reverse-biased? [2024]

(4)

Q 6 :

In the given circuit, the breakdown voltage of the Zener diode is 3.0 V. What is the value of $I_{Z}$ ? [2024]

Q 7 :

A Zener diode of breakdown voltage 10V is used as a voltage regulator as shown in the figure. The current through the Zener diode is [2024]

Q 8 :

In the given circuit, the voltage across load resistance $(R_{L})$ is [2024]

Q 9 :

In the given circuit if the power rating of Zener diode is 10 mW, the value of series resistance $R_{s}$ to regulate the input unregulated supply is [2024]

Q 10 :

A potential divider circuit is connected with a DC source of 20 V, a light-emitting diode of glow in voltage 1.8 V and a Zener diode of breakdown voltage of 3.2 V. The length (PR) of the resistive wire is 20 cm. The minimum length of PQ to just glow the LED is ____ cm. [2024]

Q 11 :

Which of the following circuits represents a forward biased diode? [2025]

Choose the correct answer from the options given below:

Q 13 :

What is the current through the battery in the circuit shown below? [2025]

Q 15 :

In the circuit shown here, assuming threshold voltage of diode is negligibly small, then voltage $V_{A B}$ is correctly represented by: [2025]

Q 16 :

A zener diode with 5 V zener voltage is used to regulate an unregulated dc voltage input of 25 V.

For a 400 $Ω$ resistor connected in series, the zener current is found to be 4 times load current. The load current $(I_{L})$ and load resistance $(R_{L})$ are: [2025]

Q 17 :

In the following circuit, the reading of the ammeter will be (Take Zener breakdown voltage = 4V) [2025]

Q 18 :

The output voltage in the following circuit is (Consider ideal diode case) [2025]

Q 22 :

Choose the correct statement about Zener diode [2023]

Q 24 :

A zener diode of power rating 1.6 W is to be used as voltage regulator. If the zener diode has a breakdown of 8 V and it has to regulate voltage fluctuating between 3 V and 10 V. The value of resistance $R_{s}$ for safe operation of diode will be [2023]

Q 25 :

If each diode has a forward bias resistance of $25 Ω$ in the below circuit,

Which of the following options is correct [2023]

Q 27 :

The charge stored by the capacitor C in the given circuit in the steady state is____________ $μ c .$ . [2026]

Q 28 :

Assuming in forward bias condition there is a voltage drop of 0.7 V across a silicon diode, the current through diode $D_{1}$ in the circuit is ______ mA.

(Assume all diodes in the given circuit are identical) [2026]

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Topic Question Set

Q 1 : Conductivity of a photodiode starts changing only if the wavelength of incident light is less than 660 nm. The band gap of photodiode is found to be (x8)eV. The value of X is (Given, h=6.6×10-34Js,e=1.6×10-19C) [2024]

Q 2 : The value of net resistance of the network as shown in the given figure is [2024]

Q 3 : Which of the diode circuit shows correct biasing used for the measurement of dynamic resistance of p-n junction diode? [2024]

Q 4 : The I-V characteristics of an electronic device shown in the figure. The device is: [2024]

Q 5 : Which of the following circuits is reverse-biased? [2024]

(4)

Q 6 : In the given circuit, the breakdown voltage of the Zener diode is 3.0 V. What is the value of IZ? [2024]

Q 7 : A Zener diode of breakdown voltage 10V is used as a voltage regulator as shown in the figure. The current through the Zener diode is [2024]

Q 8 : In the given circuit, the voltage across load resistance (RL) is [2024]

Q 9 : In the given circuit if the power rating of Zener diode is 10 mW, the value of series resistance Rs to regulate the input unregulated supply is [2024]

Q 10 : A potential divider circuit is connected with a DC source of 20 V, a light-emitting diode of glow in voltage 1.8 V and a Zener diode of breakdown voltage of 3.2 V. The length (PR) of the resistive wire is 20 cm. The minimum length of PQ to just glow the LED is ____ cm. [2024]

Q 11 : Which of the following circuits represents a forward biased diode? [2025] Choose the correct answer from the options given below:

Q 13 : What is the current through the battery in the circuit shown below? [2025]

Q 15 : In the circuit shown here, assuming threshold voltage of diode is negligibly small, then voltage VAB is correctly represented by: [2025]

Q 16 : A zener diode with 5 V zener voltage is used to regulate an unregulated dc voltage input of 25 V. For a 400 Ω resistor connected in series, the zener current is found to be 4 times load current. The load current (IL) and load resistance (RL) are: [2025]

Q 17 : In the following circuit, the reading of the ammeter will be (Take Zener breakdown voltage = 4V) [2025]

Q 18 : The output voltage in the following circuit is (Consider ideal diode case) [2025]

Q 22 : Choose the correct statement about Zener diode [2023]

Q 24 : A zener diode of power rating 1.6 W is to be used as voltage regulator. If the zener diode has a breakdown of 8 V and it has to regulate voltage fluctuating between 3 V and 10 V. The value of resistance Rs for safe operation of diode will be [2023]

Q 25 : If each diode has a forward bias resistance of 25 Ω in the below circuit, Which of the following options is correct [2023]

Q 27 : The charge stored by the capacitor C in the given circuit in the steady state is____________μc.. [2026]

Q 28 : Assuming in forward bias condition there is a voltage drop of 0.7 V across a silicon diode, the current through diode D1 in the circuit is ______ mA. (Assume all diodes in the given circuit are identical) [2026]

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Q 1 :

Conductivity of a photodiode starts changing only if the wavelength of incident light is less than 660 nm. The band gap of photodiode is found to be $(\frac{x}{8}) e V$ . The value of X is (Given, $h = 6.6 \times 10^{- 34} J s, e = 1.6 \times 10^{- 19} C$ ) [2024]

Q 2 :

The value of net resistance of the network as shown in the given figure is [2024]

Q 3 :

Which of the diode circuit shows correct biasing used for the measurement of dynamic resistance of p-n junction diode? [2024]

Q 4 :

The I-V characteristics of an electronic device shown in the figure. The device is: [2024]

Q 5 :

Which of the following circuits is reverse-biased? [2024]

Q 6 :

In the given circuit, the breakdown voltage of the Zener diode is 3.0 V. What is the value of $I_{Z}$ ? [2024]

Q 7 :

A Zener diode of breakdown voltage 10V is used as a voltage regulator as shown in the figure. The current through the Zener diode is [2024]

Q 8 :

In the given circuit, the voltage across load resistance $(R_{L})$ is [2024]

Q 9 :

In the given circuit if the power rating of Zener diode is 10 mW, the value of series resistance $R_{s}$ to regulate the input unregulated supply is [2024]

Q 10 :

A potential divider circuit is connected with a DC source of 20 V, a light-emitting diode of glow in voltage 1.8 V and a Zener diode of breakdown voltage of 3.2 V. The length (PR) of the resistive wire is 20 cm. The minimum length of PQ to just glow the LED is ____ cm. [2024]

Q 11 :

Which of the following circuits represents a forward biased diode? [2025]

Choose the correct answer from the options given below:

Q 13 :

What is the current through the battery in the circuit shown below? [2025]

Q 15 :

In the circuit shown here, assuming threshold voltage of diode is negligibly small, then voltage $V_{A B}$ is correctly represented by: [2025]

Q 16 :

A zener diode with 5 V zener voltage is used to regulate an unregulated dc voltage input of 25 V.

For a 400 $Ω$ resistor connected in series, the zener current is found to be 4 times load current. The load current $(I_{L})$ and load resistance $(R_{L})$ are: [2025]

Q 17 :

In the following circuit, the reading of the ammeter will be (Take Zener breakdown voltage = 4V) [2025]

Q 18 :

The output voltage in the following circuit is (Consider ideal diode case) [2025]

Q 22 :

Choose the correct statement about Zener diode [2023]

Q 24 :

A zener diode of power rating 1.6 W is to be used as voltage regulator. If the zener diode has a breakdown of 8 V and it has to regulate voltage fluctuating between 3 V and 10 V. The value of resistance $R_{s}$ for safe operation of diode will be [2023]

Q 25 :

If each diode has a forward bias resistance of $25 Ω$ in the below circuit,

Which of the following options is correct [2023]

Q 27 :

The charge stored by the capacitor C in the given circuit in the steady state is____________ $μ c .$ . [2026]

Q 28 :

Assuming in forward bias condition there is a voltage drop of 0.7 V across a silicon diode, the current through diode $D_{1}$ in the circuit is ______ mA.

(Assume all diodes in the given circuit are identical) [2026]