P-N Junction Diode and its applications - NEET Physics Questions
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P-N Junction Diode and its applications

Question 1: easy

What is the current through an ideal PN-junction diode shown in figure below :

1. Zero
2. 10 mA
3. 20 mA
4. 50 mA
View Answer

i = 2/100 = 20 mA 

Question 2: easy

A reverse biased diode is :

1.
2.
3.
4.
View Answer

In Reverse bias mode potential of p-type is less than that of n-type semiconductor

Question 3: easy

In the following figure, the diodes which are forward biased, are :

1. (a), (b) and (d)
2. (c) only
3. (a) and (c)
4. (b) and (d)
View Answer

For Forward biasing of PN Junction diode potential of P side should be greater than potential of N-side semiconductor

Question 4: easy

A p–n photodiode is made of a material with a band gap of 2.0 eV. The minimum frequency of the radiation that can be absorbed by the material is nearly :

1. \[1\times 10_{14} Hz\]
2. \[20\times 10_{14} Hz\]
3. \[10\times 10_{14} Hz\]
4. \[5\times 10_{14} Hz\]
View Answer

Energy of EM wave E = hυ

⇒ 2 eV = 6.626 × 10^-34×υ

⇒  \[v= 5\times 10_{14} Hz\]

Question 5: easy

When a PN junction diode is reverse biased :

1. Electrons and holes are attracted towards each other and move towards the depletion region
2. Electrons and holes move away from the junction depletion region
3. Height of the potential barrier decreases
4. No change in the current takes place
View Answer

Factual Question: When a PN junction diode is reverse biased potential barrier of depletion increases. Thus Electrons and holes move away from the junction depletion region.

Question 6: easy

The dominant mechanism for motion of charge carriers in forward and reverse biased silicon P-N junction are :

1. Drift in forward bias, diffusion in reverse bias
2. Diffusion in forward bias, drift in reverse bias
3. Diffusion in both forward and reverse bias
4. Drift in both forward and reverse bias
View Answer

Theory: In forward biased mode diffusion current is more than drift current. Where as in reverse biased mode diffusion current decreased and become less than drift current.

Question 7: easy

In the given circuit

The current through the battery is :

1. 0.5 A
2. 1 A
3. 1.5 A
4. 2 A
View Answer

Diode D2 and D3 are forward biased. Where as Diode D1 is reversed biased. No current will flow through D1. 

Equivalent Resistance= 20/3 ohm

Current = Voltage / Resistance = 10/ (20/3) = 1.5 Ampere

Question 8: easy

Phodiode, zenerdiode and solar cell is used in:

1. Forward Bias, Reverse Bias, Forward Bias
2. Reverse Bias, Reverse Bias, Unbiased
3. Reverse Bias, UnBias, Reverse Bias
4. Reverse Bias, Reverse Bias, Reverse Bias
View Answer

A Photodiode and Zener Diode operate in Reverse Bias, while a Solar Cell operates in an Unbiased condition (zero external voltage).

  • Photodiode: Works in reverse bias to detect light.
  • Zener Diode: Operates in reverse bias for voltage regulation.
  • Solar Cell: Generates power in an unbiased condition when exposed to light.
Question 9: easy

Which of the following statement is not correct when a junction diode is in forward bias :

1. The width of depletion region decrease
2. Free electrons on n-side will move towards the junction
3. Holes on p-side move towards the junction
4. Electrons on n-side and holes on p-side will move away from junction
View Answer

In forward bias, the applied field opposes the barrier field, pushing major carriers (electrons on n-side and holes on p-side) towards the junction, thereby decreasing the depletion width. Thus, statement (4) is incorrect.

Question 10: easy

The approximate ratio of resistances in the forward and reverse bias of the PN-junction diode is :

1. \(10^2 : 1\)
2. \(10^{-2} : 1\)
3. \(1 : 10^{-4}\)
4. \(1 : 10^4\)
View Answer

Forward resistance of a diode is very small (\(approx 10\Omega\)), while its reverse resistance is extremely high (\(approx 10^5 \Omega\)). The ratio \(R_f / R_r\) is of the order of \(10^{-4}\), which corresponds to \(1 : 10^4\).