The p-n Junction MCQ Quiz in తెలుగు - Objective Question with Answer for The p-n Junction - ముఫ్త్ [PDF] డౌన్‌లోడ్ కరెన్

The correct answer is option 4) i.e. voltage regulator.

CONCEPT:

• Zener diode: A Zener diode is a highly doped PN junction diode operated in reverse biased condition. 

• Since it is highly doped, the depletion layer is very thin and has a high voltage gradient and electric field.
• If the reverse-biased voltage increases, the electrons from the covalent bonds within the depletion region come out and make the depletion region conductive. This is the Zener breakdown and the voltage at this point is the Zener voltage.
• After the breakdown, there is a sharp increase in the reverse current irrespective of the external voltage supplied.

EXPLANATION:

• The Zener diode conducts only at a voltage greater than the Zener voltage. 
• The voltage across the Zener diode does not change even if the external source voltage is increased. 
• This helps in regulating the voltage fluctuations and therefore it is used as a voltage regulator.

CONCEPT:

• The material which is not a good conductor or a good insulator is called a semiconductor.
  • For example: Silicon, Germanium, etc.
• The semiconductor device which is used to control the flow of electric current is called a p-n junction diode.

• The depletion region/layer is an area at the junction where a field is formed because of the formation of a negative charge layer on the p side and a positive charge layer on the n side

EXPLANATION:

• A depletion region or depletion layer is a region in a P-N junction diode where no mobile charge carriers are present. 

• The depletion layer acts like a barrier that opposes the flow of electrons from the n-side and holes from the p-side.

• Therefore, the depletion layer at a p-n junction contains both positive and negative immobile charges.

• Hence option 4 is correct.

CONCEPT:

• Semiconductor: A solid substance that has a conductivity between an insulator and metals.
  • Semiconductors have conductivity due to many factors like the addition of an impurity or because of temperature effects.
• N-type semiconductors: An extrinsic semiconductor where the dopant atoms provide extra conduction electrons to the host material like Phosphorus P in Silicon Si.
  • This creates an excess of negative (n-type) electron charge carriers that are able to move freely.

• P-type semiconductors: A semiconductor, when the impurity with trivalency is added to pure semiconductors, then it is known as a p-type semiconductor.
  • Impurities with trivalency such as Boron (B), Gallium (Ga), Indium(In), Aluminium(Al), etc are called acceptor impurity.

EXPLANATION:

• P-type and N-type materials are NOT positively and negatively charged. 
  • because atoms are electrically neutral.

• ​N-type materials have electrons or negative charges that are majority carriers and holes are minority carriers. So it has mainly electrons or negative charge carriers that can move freely, but it is still neutral because the fixed donor atoms, having donated electrons, are positive.
• So the correct answer will be option 4.

CONCEPT:

Diode: 

• A diode is a semiconductor device that essentially acts as a one-way switch for current.
• It allows current to flow easily in one direction but severely restricts current from flowing in the opposite direction.

• Depletion region:
  • ​When the p-type and the n-type materials are kept in contact with each other, the junction between them behaves differently from either side of the material alone.
  • The electrons and holes are close to each other at the junction. According to coulomb’s law, there is a force between the negative electrons and the positive holes.
  • When the p-n junction is formed a few electrons from the n-type diffuse through the junction and combines with the holes in the p-side to form negative ions and leaves behind positive ions in the n-side.
  • This results in the formation of the depletion layer, which acts as the barrier and does not allow any further flow of electrons from the n region to the p region.

EXPLANATION:

• In a p-n junction, there exists a concentration difference of charge carriers in the given junctions.
• A covalent bond is formed when an electron from the n-section diffuses into the p-section in a process called electron-hole recombination.
• Accumulation of electric charges of opposite polarities creates a potential barrier between the two sections of the junction.
• This electric field setting up a potential barrier in the junction which opposes further diffusion is due to the fixed acceptor and donor ions on either side of the junction.
• Hence, option 4 is correct.

The correct answer is option 3) i.e. 2 × 106 Ω.

CONCEPT:

• Diode: A diode is a two-terminal semiconductor device that acts as a one-way switch for current.
  • The diode allows current to flow in one direction easily and restricts current flowing in the opposite direction.
  • An ideal diode has zero resistance in one direction, and infinite resistance in the reverse direction.​​
• Reverse bias: In reverse bias, the n-type material is connected to the positive terminal of the battery and the p-type material is connected to the negative terminal of the battery.​​​ 
  • When a diode is reverse biased, the voltage at the cathode is higher than that at the anode. Therefore, no current will flow which means that the resistance is greater.

CALCULATION:

Give that:

The change in the applied voltage (\(\Delta V\)) = 1 V

The change in current (\(\Delta I\)) = 0.5 μA = 0.5 \(\times\) 10^-6 A

Using Ohm's law, V = IR

\(\Rightarrow\)\(\Delta V = \Delta (IR)\)

\(\Delta V = ​​\Delta I \times R\)          (\(\because\) R is fixed for a material at given temperature)

1 volt = 0.5 \(\times\) 10-6  \(\times\)R

Resistance, R = 2 × 106 Ω

Additional Information

• In forward bias, the n-type material is connected to the negative terminal of the battery, and the p-type material is connected to the positive terminal of the battery.​​​ 
• Therefore, the current will flow easily which means that the resistance is lower.
• In forward biasing the diode operates as a conductor whereas in reverse bias the diode acts as an insulator.

CONCEPT:

• Doping: The process of adding impurities to a pure (intrinsic) semiconductor is called doping.
  • By doing this, the conductivity of the semiconductor is increased drastically even at room temperatures.
  • It is needed because the conductivity of a pure semiconductor like silicon or germanium is very low at room temperatures.
  • Doping leads to the formation of extrinsic semiconductors which are of two types: n-type and p-type.
• N-type semiconductors have impurities of elements from Group 5 of the periodic table, hence electrons are the majority charge carriers.
• P-type semiconductors have impurities of elements from Group 3 of the periodic table, hence holes are the majority charge carriers.

​EXPLANATION:

• From the given options Boron is the only element in group 13, a p-type semiconductor is made when 14^th group element is doped with 13^th group. Hence, option 1 is the answer

CONCEPT:

• Rectification: A rectifier is a device that converts alternating current (AC) into a direct current (DC). This process is called rectification.
  • A p-n junction diode can be used as a rectifier because it permits current in one direction only.
• A triode is a vacuum tube with three electrodes which are a cathode, Anode, and a control grid.
• The thermocouple is an electrical device containing junctions of two dissimilar metal joints. It is used as temperature sensors.
• Transistor: A semiconductor device used to amplify or switch electronic signals and electrical power is called a transistor.

EXPLANATION:

• Since a p-n junction diode is used as a rectifier to rectify alternating current.
• That's why in order to rectify an alternating current one uses a diode. So option 2 is correct.

CONCEPT:

• Semiconductors: The materials that have a conductivity between conductors and insulators are called semiconductors.
• n-type semiconductor: A n-type semiconductor is produced by doping a 14 group element with a 15 group element.
• p-type semiconductor: A p-type semiconductor is produced by doping a 14 group element with a 13 group element.
  • 14 group element has 4 valence electron whereas that of group 13 has 3 valence electron.
  • For example, doping germanium with gallium forms a p-type semiconductor because Germanium is a 14 group element and gallium is a 13 group element, thus 

• Bismuth is the 15th Group element.

EXPLANATION:

• According to the definition of the p-type semiconductor, a p-type semiconductor is produced by doping a 14 group element with a 13 group element.
• Gallium is the 13th Group element. So, when Gallium is doped with Germanium, it will form a p-type semiconductor. So the correct answer is option 3.

Concept:

P-N junction diode:

• A P-N junction is an interface or a boundary between two semiconductor material types, namely the p-type and the n-type, inside a semiconductor.
• A P-N junction diode is a two-terminal semiconductor device that is used for allowing electric current in one direction.

There are two operating regions in the P-N junction diode: ​

1. P-type 
2. N-type

There are three biasing conditions for the P-N junction diode, and this is based on the voltage applied:

• Zero bias: No external voltage is applied to the P-N junction diode.
• Forward bias:
  • The positive terminal of the voltage potential is connected to the p-type while the negative terminal is connected to the n-type.
  • During forward bias, the width of the depletion region decreases, and the barrier height is reduced.
• 

Explanation:

The positive terminal of the voltage potential is connected to the p-type while the negative terminal is connected to the n-type.

In the above diagram, the positive terminal is connected with the P-side and the negative terminal is connected with the n side of the diode.

Additional InformationReverse bias:

• The negative terminal of the voltage potential is connected to the p-type and the positive is connected to the n-type.
• During reverse bias, the width of the depletion region increases, and the barrier height increases.

V-I characteristics of P-N junction diode: 

• VI characteristics of P-N junction diodes is a curve between the voltage and current through the circuit
• 

Concept:

• A tunnel diode is a highly doped semiconductor diode.
• The p-type and n-type semiconductor is heavily doped in a tunnel diode due to a greater number of impurities. Heavy doping results in a narrow depletion region.
• When compared to a normal p-n junction diode, tunnel diode has a narrow depletion width.
• The Fermi level moves in the conduction band on the n-side and inside the valence band on the p-side.
• Below the Fermi level, all states are filled and above the Fermi level all states are empty

Tunnel diode is represented by the symbol

Explanation-

• A tunnel diode is also known as Esaki diode as it was invented by Leo Esaki in August 1957. Basically, it is a heavily doped p-n junction semiconductor and is capable of very fast operation.
• The tunnel diode shows negative resistance when the voltage value increases by decreasing the flow of current. Tunnel diode works based on the tunnel Effect.