The Junction Rectifier MCQ Quiz - Objective Question with Answer for The Junction Rectifier - Download Free PDF

Correct option is: (2) D₁ is reverse biased, D₂ is forward biased

V_in = 220 × sin(100πt) volt

Given: t = 15 ms = 0.015 s

ω = 100π

2π / T = 100π

⇒ T = 1 / 50 s

⇒ T = 0.02 s

Now, t = (3T / 4)

i.e., the signal is in the negative half cycle.

So now the negative half cycle is fed to the circuit, making D₁ reverse biased and D₂ forward biased.

Explanation: 

The most widely used rectifier is the Bridge full-wave rectifier. This is because it has several advantages over other types of rectifiers. The bridge full-wave rectifier utilizes four diodes arranged in a bridge configuration to convert the entire AC waveform into a pulsating DC waveform.

Advantages of Bridge Full-Wave Rectifier:

• Higher Efficiency: It provides higher efficiency compared to half-wave and center-tap full-wave rectifiers because it uses the entire AC waveform.
• No Center Tap Required: It does not require a center-tap transformer, which simplifies its design and reduces cost.
• Better Transformer Utilization: The transformer utilization factor is higher compared to center-tap full-wave rectifiers.
• Smoother Output: It produces a smoother output waveform with less ripple, making it more suitable for sensitive electronic devices.

Therefore, the correct answer is option 3.

Calculatoin:

A full-wave rectifier inverts the negative half cycles of the input AC signal. Thus, the frequency of the ripple will be double the frequency of the input AC signal.

Given that the input AC mains frequency is 50 Hz, for a full-wave rectifier, the fundamental frequency in the ripple output will be:

f_ripple = 2 × f_input = 2 × 50 Hz = 100 Hz

Therefore, the fundamental frequency in the ripple output will be 100 Hz.

Concept and Explanation:

• A rectifier converts alternating current to direct current
• The process of converting alternating current (AC) into direct current(DC) is called rectification.
• Diode is used as a rectifier for converting alternating current into direct current.
• A p-n junction is generally called a p-n junction diode since the current flows in a unidirectional manner and hence makes the diode suitable to use as a rectifier.
• There are two ways of using a diode as a rectifier,

1. Diode as half-wave rectifier
2. Diode as full wave rectifier

Diode as half-wave rectifier

• In half wave rectification, either the positive or negative half of the AC wave is passed, while the other half is blocked.

Diode as full wave rectifier

• A full-wave rectifier converts the whole of the input waveform to one of constant polarity (positive or negative) at its output.
• Full-wave rectification converts both polarities of the input waveform to DC (direct current),

Additional Information

•  The process of increasing the volume of sound, especially using an amplifier is called amplification​

CONCEPT:

Rectifier:

• A rectifier is a device which converts an alternating current into a direct current. A p-n junction can be used as a rectifier because it permits current in one direction only.
• There are types of rectifier i.e. half wave rectifier and full wave rectifier.

EXPLANATION:

• From above it is clear that a p-n junction can be used as a rectifier because it permits current in one direction only. Therefore option 2 is correct.
• A junction transistor is formed by sandwiching a thin layer of a p-type semiconductor between two layers of an n-type semiconductor or by sandwiching a thin layer of a n-type semiconductor between two layers of an p-type semiconductor. Therefore option 1 is incorrect.
• A device which increases the amplitude of the input signal is called amplifier. Therefore option 3 is incorrect.
• An oscillator is an electronic circuit that generates sinusoidal oscillations known as sinusoidal oscillator. It converts input energy from a DC source into AC output energy of periodic waveform, at a specific frequency and is known amplitude. Therefore option 4 is incorrect.

CONCEPT:

Rectifier:

• A rectifier is a device that converts an alternating current into a direct current. A p-n junction can be used as a rectifier because it permits current in one direction only.
  • There are types of rectifier i.e. half-wave rectifier and full-wave rectifier.
• In a full-wave rectifier during a positive half cycle, one diode conducts and gives the output similarly in the negative half cycle another diode conducts and gives the output. Hence at a time, only one diode will be ON for one-half cycle. 
  • In the case of the full-wave rectifier, the fundamental frequency = 2 × main frequency. 

CALCULATION:

Given - Main frequency = 50 Hz

• In the case of the full-wave rectifier,

⇒ Fundamental frequency = 2 × main frequency

⇒ Fundamental frequency = 2 × 50 = 100 Hz

CONCEPT:

• Alternating current: The electric current whose direction changes periodically is called electric current.
• Direct current (DC): The electric current whose direction remains the same always is called direct current.
• Rectifier: A rectifier is a device that converts an alternating current into a direct current.
  • A p-n junction can be used as a rectifier because it permits current in one direction only.

EXPLANATION:

1. A rectifier is an electrical device that converts alternating current (AC), which periodically reverses direction, to direct current (DC), which flows in only one direction. So option 1 is correct.
2. A dynamo makes direct current electric power using electromagnetism. 
3. An ammeter measures the amount of current flowing through a circuit. A motor converts electrical energy into mechanical energy.
4. A motor converts electrical energy into mechanical energy. 

The correct answer is option 1) i.e. 100 Hz

CONCEPT:

• Full-wave rectifiers: A full-wave rectifier is a rectifier circuit that converts alternating current to direct current, and allows both the positive and negative cycles of the AC cycle to pass through it using diodes.
  • Full-wave rectifiers use multiple diodes. A diode is used because a diode can conduct current only in one direction at a particular instant of time
  • AC current can be represented as a waveform and a wave is said to complete one cycle when the wave pattern repeats. The frequency is associated with one complete cycle of a wave.

• From the figure, the output wave completes one cycle in half the time taken by input to complete one cycle.
• Therefore, the output frequency in a full-wave rectifier is equal to 2 times the input frequency.

​EXPLANATION:

The given frequency of the input = 50 Hz

The fundamental frequency of the output ripples = 2 times the input frequency = 2 × 50 = 100 Hz. 

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 device that increases the amplitude of the input signal is called an amplifier.
  • An n-p-n or p-n-p transistor is used as a transistor to increase the amplitude of the input signal.

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 1 is correct.
• In an amplifier, indicator, and modulator, a transistor is used. Therefore option 2, 3, and 4 is incorrect.

The correct answer is option 2) i.e. 50 Hz.

CONCEPT:

Half-wave rectifiers: 

• A half-wave rectifier is a rectifier circuit that converts alternating current to direct current and allows only half of the AC cycle to pass through it using diodes.
• Half-wave rectifiers use a single diode and full-wave rectifiers use multiple diodes. A diode is used because a diode can conduct current only in one direction at a particular instant of time.

EXPLANATION:

• In a have wave rectifier, either the positive or negative half cycles are obtained as the output.
• AC current can be represented as a waveform and a wave is said to complete one cycle when the wave pattern repeats. The frequency is associated with one complete cycle of a wave.

​

From the figure, the output waveform completes one cycle at the same time as that of the input waveform. Therefore, the frequency of the output wave is equal to the frequency of the input wave.

Hence, the output frequency is 50 Hz.

Additional Information

• In a full-wave rectifier, the output wave completes one cycle in half the time taken by input to complete one cycle. Therefore, the output frequency in a full-wave rectifier is equal to 2 times the input frequency.

CONCEPT:

• A rectifier is a device that converts an alternating current into a direct current.
• A p-n junction can be used as a rectifier because it permits current in one direction only.

EXPLANATION:

• There are types of rectifiers i.e. half-wave rectifier and full-wave rectifier.
• In a half-wave rectifier, there is only one diode, so during a positive half cycle diode conducts and gives the output similarly in the negative half cycle diode don’t conduct and gives no output.
• In a full-wave rectifier during a positive half cycle, one diode conducts and gives the output similarly in the negative half cycle another diode conducts and gives the output. Hence at a time, only one diode will be ON for one-half cycle.

CONCEPT:

A rectifier which is used to convert ac voltage into dc voltage is called full wave rectifier.

• In a full-wave rectifier, during the positive half cycle, one diode conducts and gives the output similarly in the negative half cycle another diode conducts and gives the output.
• In half-wave rectifier, there is only one diode, so during the positive half cycle diode conducts and gives the output similarly in the negative half cycle diode don’t conduct and gives no output.

• Inductor is used to strore energy in DC-AC convertor. It stores the energy and full fill the energy when there is needed and convert the pulsating voltage into a DC source.
  • It is connected in the series with the load.

Explanation:

• The rectified voltage output from a full wave rectifier is in the form of pulses of the shape of half sinusoids. To get steady DC output from the pulsating voltage.

CONCEPT:

• A rectifier which is used to convert ac voltage into dc voltage is called full wave rectifier.

• In a full-wave rectifier, during the positive half cycle, one diode conducts and gives the output similarly in the negative half cycle another diode conducts and gives the output.
• In half-wave rectifier, there is only one diode, so during the positive half cycle diode conducts and gives the output similarly in the negative half cycle diode don’t conduct and gives no output.

EXPLANATION:

• The full wave rectifier converts ac voltage into dc voltage. So statement 1 is correct and statement 4 is wrong. Hence option 4 is correct.
• The power loss by a full wave rectifier is very less compared to half wave rectifier. So statement 2 is correct.
• The efficiency of full wave rectifier is higher compared to half wave rectifier. So statement 3 is correct.

CONCEPT:

• A rectifier is a device that converts an alternating current into a direct current.
• A p-n junction can be used as a rectifier because it permits current in one direction only.

EXPLANATION:

• A rectifier is an electrical device that converts alternating current (AC), which periodically reverses direction, to direct current (DC), which flows in only one direction. So option 4 is correct.

CONCEPT:

• A rectifier is a device that converts an alternating current into a direct current.
• A p-n junction can be used as a rectifier because it permits current in one direction only.

Ripple factor:

• The ripple factor of a rectifier is defined as the ratio of the value of a.c. component to the value of d.c. component.

\({\rm{Ripple\;factor}} = \frac{{{I_{a.c.}}}}{{{I_{d.c.}}}} = \frac{{{E_{a.c.}}}}{{{E_{d.c.}}}} = \sqrt {{{\left( {\frac{{{I_{r.m.s.}}}}{{{I_{d.c.}}}}} \right)}^2} - 1} \)

• Thus if the ripple factor is less, the power supply has less AC components and power supply output is purer (i.e more DC without much fluctuations)
• Thus ripple factor is an indication of the purity of output of power supply.

EXPLANATION:

• From the above table, it is clear that the Bridge wave rectifier has a 0.48 ripple factor.