Electronic Devices | Physics JEE previous year questions with Solutions

Q 11 :

In the DC voltage regulator circuit shown, the Zener breakdown voltage $V_{Z}$ = 5 V. If the unregulated input varies between 11 V to 15 V, maximum zener current (in mA) is

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(3)

$Zener current will be maximum, when V = 15 V, 15 - (i \times 2.5 k) = 5, i = 4 m A, i_{z} = 3 m A$

Q 12 :

Assertion: The photodiode is used to detect the optical signals. These diodes are preferably operated in reverse biased mode

Reason: fractional change in majority carriers produce higher reverse bias current

Assertion is True, Reason is True; Reason is a Correct explanation for Assertion
Assertion is True, Reason is True; Reason is NOT a Correct explanation for Assertion
Assertion is True, Reason is False
Assertion is False, Reason is True

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(3)

A photodiode is reverse biased. When light falling on it produces charge carriers, the fractional change, in minority carriers is high since the original current is very small.

$T E (2 R) = - \frac{G M m}{4 R}$

$T E (3 R) = - \frac{G M m}{6 R}$

Q 13 :

The reverse breakdown voltage of a Zener diode is 5.6 V in the given circuit. The current $I_{z}$ through the Zener is:

10 mA
17 mA
15 mA
7 mA

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(1)

$P.D. across 800 Ω resistors = 5.6 V$

$So, I_{800 Ω} = \frac{5.6}{800} A = 7 m A$

$Now, P.D. across 200 Ω resistors$

$= 9 - 5.6 V = 3.4 V$

$So, I_{200 Ω} = \frac{9 - 5.6}{200} = 17 m A$

$So, current through zener diode = I_{Z} = 17 - 7 = 10 m A$

Q 14 :

For the given logic circuit, which of the following inputs combination will make both LED-1 and LED-2 to glow? [2026]

A = 0, B = 1, C = 1
A = 1, B = 0, C = 0
A = 1, B = 0, C = 1
A = 0, B = 1, C = 0

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(3)

$option (1) \Rightarrow A = 0, B = 1, C = 1$

$x = 1, y = 0$

$both will not glow$

$option (2) \Rightarrow A = 1, B = 0, C = 0$

$x = 1, y = 0$

$will not glow$

$option (3) \Rightarrow A = 1, B = 0, C = 1$

$x = 1, y = 1$

$both will glow$

Q 15 :

For the given circuit (shown in part (A)), the time dependent input voltage $v_{i n} (t)$ and corresponding output $v_{o} (t)$ are shown in part (B) and part (C), respectively. Identify the components that are used in the circuit between points X and Y. [2026]

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(2)

For the +ve half cycle of input: Middle branch has ideal diode in forward bias and Zener diode in reverse bias. Thus, we get constant 5 V output due to Zener breakdown. For this situation component between X and Y should act as open circuit.

For −ve half cycle of input: Middle branch has ideal diode in reverse bias, which makes it open branch without any current. For this situation component between X and Y should give a constant −5 V output due to Zener breakdown.

(Note: The input side must contain some resistance else $V_{i n}$ is equal to $V_{o u t}$ for every cases)

Q 16 :

Consider a circuit consisting of a capacitor (20 $μF$ ), resistor (100 $Ω$ ) and two identical diodes as shown in figure. The resistance of diode under forward biasing condition is 10 $Ω$ . The time constant of the circuit is $α \times 10^{- 3} s$ . The value of $α$ is ________. [2026]

2.2
2.0
2.1
2.4

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(1)

$τ = R C$

$τ = (110) \times 20 \times 10^{- 6} \sec$

$τ = 2200 \times 10^{- 6} \sec$

$τ = 2.2 \times 10^{- 3} \sec$

Q 17 :

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

Assertion A: A diode under reverse-biased condition provides very small current which is nearly independent of voltage until a critical limit at which the current increases drastically.

Reason R: Below the critical voltage limit, only majority charge carriers flow which increases drastically above critical voltage.

Choose the correct answer from the options given below. [2026]

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

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(3)

Assertion is true: in reverse biased condition current is very small as only minority charge carries flows which will increase drastically after crossing breakdown voltage critical limit but Reason is false.

Q 18 :

The maximum rated power of the LED is 2 mW and it is used in the circuit with input voltage of 5 V as shown in the figure below. The current through resistance $R_{s}$ is 0.5 mA.

The minimum value of the resistance of $R_{s}$ , to ensure that the LED is not damaged is ________ $k Ω$ . [2026]

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(2)

$A diode in reverse bias has no current flowing through it.$

$P_{bulb} = 2 \times 10^{- 3}$

$V_{bulb} = 4 V$

$So 5 V = V_{R s} + V_{bulb}$

$V_{R s} = 5 - 4 = 1 V$

$1 = 0.5 \times 10^{- 3} R_{s} \Rightarrow R_{s} = 2 k Ω$

Q 19 :

A diode has Zener voltage of 10 V and maximum power dissipation of 0.5 W, then the minimum resistance to be used in series with this diode for safety when it is connected to a 25 V power supply is _____ $Ω$ . [2026]

(300)

$P_{Max} = V_{Z} I_{Z}$

$\Rightarrow I_{Z} = \frac{P_{Max}}{V_{Z}} = \frac{0.5}{10} = 0.05 A$

$V_{R} = V_{s} - V_{z} = 25 - 10 = 15 V$

$R_{\min} = \frac{V_{R}}{I_{Z}} = \frac{15.0}{0.05} = 300 Ω$

Topic Question Set

Q 11 :

In the DC voltage regulator circuit shown, the Zener breakdown voltage $V_{Z}$ = 5 V. If the unregulated input varies between 11 V to 15 V, maximum zener current (in mA) is

Q 12 :

Assertion: The photodiode is used to detect the optical signals. These diodes are preferably operated in reverse biased mode

Reason: fractional change in majority carriers produce higher reverse bias current

Q 13 :

The reverse breakdown voltage of a Zener diode is 5.6 V in the given circuit. The current $I_{z}$ through the Zener is:

Q 14 :

For the given logic circuit, which of the following inputs combination will make both LED-1 and LED-2 to glow? [2026]

Q 15 :

For the given circuit (shown in part (A)), the time dependent input voltage $v_{i n} (t)$ and corresponding output $v_{o} (t)$ are shown in part (B) and part (C), respectively. Identify the components that are used in the circuit between points X and Y. [2026]

Q 16 :

Consider a circuit consisting of a capacitor (20 $μF$ ), resistor (100 $Ω$ ) and two identical diodes as shown in figure. The resistance of diode under forward biasing condition is 10 $Ω$ . The time constant of the circuit is $α \times 10^{- 3} s$ . The value of $α$ is ________. [2026]

Q 19 :

A diode has Zener voltage of 10 V and maximum power dissipation of 0.5 W, then the minimum resistance to be used in series with this diode for safety when it is connected to a 25 V power supply is _____ $Ω$ . [2026]

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Topic Question Set

Q 11 : In the DC voltage regulator circuit shown, the Zener breakdown voltage VZ = 5 V. If the unregulated input varies between 11 V to 15 V, maximum zener current (in mA) is

Q 12 : Assertion: The photodiode is used to detect the optical signals. These diodes are preferably operated in reverse biased mode Reason: fractional change in majority carriers produce higher reverse bias current

Q 13 : The reverse breakdown voltage of a Zener diode is 5.6 V in the given circuit. The current Iz through the Zener is:

Q 14 : For the given logic circuit, which of the following inputs combination will make both LED-1 and LED-2 to glow? [2026]

Q 15 : For the given circuit (shown in part (A)), the time dependent input voltage vin(t) and corresponding output vo(t) are shown in part (B) and part (C), respectively. Identify the components that are used in the circuit between points X and Y. [2026]

Q 16 : Consider a circuit consisting of a capacitor (20 μF), resistor (100 Ω) and two identical diodes as shown in figure. The resistance of diode under forward biasing condition is 10 Ω. The time constant of the circuit is α×10-3s. The value of α is ________. [2026]

Q 18 : The maximum rated power of the LED is 2 mW and it is used in the circuit with input voltage of 5 V as shown in the figure below. The current through resistance Rs is 0.5 mA. The minimum value of the resistance of Rs, to ensure that the LED is not damaged is ________ kΩ. [2026]

Q 19 : A diode has Zener voltage of 10 V and maximum power dissipation of 0.5 W, then the minimum resistance to be used in series with this diode for safety when it is connected to a 25 V power supply is _____ Ω. [2026]

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Q 11 :

In the DC voltage regulator circuit shown, the Zener breakdown voltage $V_{Z}$ = 5 V. If the unregulated input varies between 11 V to 15 V, maximum zener current (in mA) is

Q 12 :

Assertion: The photodiode is used to detect the optical signals. These diodes are preferably operated in reverse biased mode

Reason: fractional change in majority carriers produce higher reverse bias current

Q 13 :

The reverse breakdown voltage of a Zener diode is 5.6 V in the given circuit. The current $I_{z}$ through the Zener is:

Q 14 :

For the given logic circuit, which of the following inputs combination will make both LED-1 and LED-2 to glow? [2026]

Q 15 :

For the given circuit (shown in part (A)), the time dependent input voltage $v_{i n} (t)$ and corresponding output $v_{o} (t)$ are shown in part (B) and part (C), respectively. Identify the components that are used in the circuit between points X and Y. [2026]

Q 16 :

Consider a circuit consisting of a capacitor (20 $μF$ ), resistor (100 $Ω$ ) and two identical diodes as shown in figure. The resistance of diode under forward biasing condition is 10 $Ω$ . The time constant of the circuit is $α \times 10^{- 3} s$ . The value of $α$ is ________. [2026]

Q 19 :

A diode has Zener voltage of 10 V and maximum power dissipation of 0.5 W, then the minimum resistance to be used in series with this diode for safety when it is connected to a 25 V power supply is _____ $Ω$ . [2026]