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Physics NCERT Exemplar Solutions Class 12th Chapter Fourteen

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4 months ago

Physics NCERT Exemplar Solutions Class 12th Chapter Fourteen Semiconductor Electronics

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

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alok kumar singh

Contributor-Level 10

This is a Multiple Choice Questions as classified in NCERT Exemplar

Answer- d

Explanation- as we know that Ev = E_o/ $\sqrt[]{2}$ so E₀= Ev $\sqrt[]{2}$ so net voltage is 220 $\sqrt[]{2}$ V

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Physics NCERT Exemplar Solutions Class 12th Chapter Fourteen Semiconductor Electronics

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

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alok kumar singh

Contributor-Level 10

This is a Multiple Choice Questions as classified in NCERT Exemplar

Answer-b

Explanation- from the figure we can say that diode D1 is reverse biased and diode D2 is forward biased so current will flow from B to A.

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Physics NCERT Exemplar Solutions Class 12th Chapter Fourteen Semiconductor Electronics

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

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alok kumar singh

Contributor-Level 10

This is a Multiple Choice Questions as classified in NCERT Exemplar

Explanation - When p-n junction is forward biased, it opposes the potential barrier junction, when p-n junction is reverse biased, it supports the potential barrier junction, resulting increase in potential barrier across the junction.

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Physics NCERT Exemplar Solutions Class 12th Chapter Fourteen Semiconductor Electronics

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

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alok kumar singh

Contributor-Level 10

This is a Multiple Choice Questions as classified in NCERT Exemplar

Answer- (d)

Explanation- when we increase temperature conductivity increases because number density is increasing after increasing temperature which decreases the relaxation time

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Physics NCERT Exemplar Solutions Class 12th Chapter Fourteen Semiconductor Electronics

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)?

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alok kumar singh

Contributor-Level 10

This is a Short Answer Type Questions as classified in NCERT Exemplar

Explanation- power = 1W

Zener breakdown voltage = 5V

Minimum voltage = 3V

Maximum voltage = 7V

Current = power/voltage= 1/5=0.2A

The value of R for safe operation would be R = max voltage – Zener voltage/current

= 7- 5/0.2 = 2/0.2 = 10ohm

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Physics NCERT Exemplar Solutions Class 12th Chapter Fourteen Semiconductor Electronics

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

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alok kumar singh

Contributor-Level 10

This is a Short Answer Type Questions as classified in NCERT Exemplar

Explanation- this is AND GATE so truth table for this will be

A	B	A.B
0	0
0	1	0
1	0	1
1	1

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Physics NCERT Exemplar Solutions Class 12th Chapter Fourteen Semiconductor Electronics

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

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alok kumar singh

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This is a Short Answer Type Questions as classified in NCERT Exemplar

Explanation- In elemental semiconductor, the band gap is such that the emission are in infrared region and not in visible region.

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Physics NCERT Exemplar Solutions Class 12th Chapter Fourteen Semiconductor Electronics

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

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alok kumar singh

Contributor-Level 10

This is a Short Answer Type Questions as classified in NCERT Exemplar

Explanation- The NOT GATE is a device which has only one input and one output i.e., A'=Y means Y equals NOT A.

This GATE cannot be realised by using diodes. However it can be realised by making use of a

transistor. This can be seen in the figure given below.

A	Y
0	1
1	0

Here, the base B of the transistor is connected to the input A through a resistance Rb and the emitter E is earthed. The collector is connected to 5 V battery. The output Y is the voltage at C w.r.t. earth.

The resistor Rb and Rc are so chosen that if emitter-base junction is unbiased, the transistor is in

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Physics NCERT Exemplar Solutions Class 12th Chapter Fourteen Semiconductor Electronics

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.