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When an SCR is in forward blocking mode, the applied voltage
- a)appears across only one junction
- b)is equally shared by two junctions
- c)is equally shared by three junctions
- d)may appear across one or more junctions
Correct answer is option 'A'. Can you explain this answer?
Most Upvoted Answer
When an SCR is in forward blocking mode, the applied voltagea)appears ...
Introduction:
In an SCR (Silicon Controlled Rectifier), forward blocking mode is one of the four operating modes. In this mode, the SCR is reverse biased, and no conduction occurs. The applied voltage appears across only one junction of the SCR.
Explanation:
When an SCR is in forward blocking mode, the following points explain why the applied voltage appears across only one junction:
1. Reverse Biased:
In forward blocking mode, the SCR is reverse biased, which means the anode terminal is at a higher voltage potential compared to the cathode terminal. This reverse biasing prevents the flow of current through the SCR, and it remains in the off state.
2. Junctions in an SCR:
An SCR consists of three layers - P-N-P or N-P-N, forming two junctions. The middle layer is called the base or the control layer, while the other two layers are called the anode and cathode layers.
3. Forward Blocking Voltage:
The applied voltage in the forward blocking mode is a reverse voltage, also known as the forward blocking voltage (Vfbo). This voltage is applied between the anode and cathode terminals of the SCR.
4. Junction Behavior:
When a reverse voltage is applied across the SCR, the two junctions behave differently:
- Anode Junction: The anode junction is forward biased in the reverse voltage condition. This means the voltage drop across this junction is relatively low, and it allows a small leakage current to flow.
- Cathode Junction: The cathode junction is reverse biased in the reverse voltage condition. This means the voltage drop across this junction is high, and it prevents the flow of current.
5. Voltage Distribution:
Due to the different behaviors of the two junctions, the applied voltage is primarily dropped across the cathode junction. This is because the cathode junction is reverse biased and offers a higher resistance to the flow of current compared to the anode junction.
Conclusion:
In conclusion, when an SCR is in forward blocking mode, the applied voltage appears across only one junction, mainly the cathode junction. This is because the cathode junction is reverse biased and offers a higher resistance, preventing the flow of current through the SCR.
In an SCR (Silicon Controlled Rectifier), forward blocking mode is one of the four operating modes. In this mode, the SCR is reverse biased, and no conduction occurs. The applied voltage appears across only one junction of the SCR.
Explanation:
When an SCR is in forward blocking mode, the following points explain why the applied voltage appears across only one junction:
1. Reverse Biased:
In forward blocking mode, the SCR is reverse biased, which means the anode terminal is at a higher voltage potential compared to the cathode terminal. This reverse biasing prevents the flow of current through the SCR, and it remains in the off state.
2. Junctions in an SCR:
An SCR consists of three layers - P-N-P or N-P-N, forming two junctions. The middle layer is called the base or the control layer, while the other two layers are called the anode and cathode layers.
3. Forward Blocking Voltage:
The applied voltage in the forward blocking mode is a reverse voltage, also known as the forward blocking voltage (Vfbo). This voltage is applied between the anode and cathode terminals of the SCR.
4. Junction Behavior:
When a reverse voltage is applied across the SCR, the two junctions behave differently:
- Anode Junction: The anode junction is forward biased in the reverse voltage condition. This means the voltage drop across this junction is relatively low, and it allows a small leakage current to flow.
- Cathode Junction: The cathode junction is reverse biased in the reverse voltage condition. This means the voltage drop across this junction is high, and it prevents the flow of current.
5. Voltage Distribution:
Due to the different behaviors of the two junctions, the applied voltage is primarily dropped across the cathode junction. This is because the cathode junction is reverse biased and offers a higher resistance to the flow of current compared to the anode junction.
Conclusion:
In conclusion, when an SCR is in forward blocking mode, the applied voltage appears across only one junction, mainly the cathode junction. This is because the cathode junction is reverse biased and offers a higher resistance, preventing the flow of current through the SCR.
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Community Answer
When an SCR is in forward blocking mode, the applied voltagea)appears ...
Forward Blocking Mode of an SCR
In the forward blocking mode of a Silicon Controlled Rectifier (SCR), the SCR is reverse biased, meaning that the anode is at a higher potential than the cathode. In this mode, the SCR is designed to block the flow of current through it.
Explanation of the Answer
The correct answer to the given question is option 'A', which states that when an SCR is in forward blocking mode, the applied voltage appears across only one junction. This means that the entire applied voltage is dropped across a single junction within the SCR.
Reasoning
To understand why the voltage appears across only one junction, it is important to understand the structure of an SCR.
Structure of an SCR
An SCR is a four-layer, three-junction semiconductor device. The layers are named P1, N1, P2, and N2, starting from the anode side. The three junctions are J1, J2, and J3, as shown below:
J1: P1-N1 Junction
J2: P2-N1 Junction
J3: P2-N2 Junction
Explanation
When the SCR is in forward blocking mode, the anode is at a higher potential compared to the cathode. This causes J1 and J2 to be reverse biased, while J3 is forward biased.
In this mode, the depletion layers at J1 and J2 become wider, preventing the flow of current through these junctions. However, the depletion layer at J3 becomes narrower, allowing the flow of current through it.
Since the entire applied voltage is dropped across J3, the voltage appears across only one junction. This is because the other two junctions, J1 and J2, are reverse biased and do not allow the applied voltage to be dropped across them.
Therefore, in forward blocking mode, the applied voltage appears across only one junction, which is J3.
Conclusion
When an SCR is in forward blocking mode, the applied voltage appears across only one junction, specifically J3. This is because J1 and J2 are reverse biased and do not allow the voltage to be dropped across them.
In the forward blocking mode of a Silicon Controlled Rectifier (SCR), the SCR is reverse biased, meaning that the anode is at a higher potential than the cathode. In this mode, the SCR is designed to block the flow of current through it.
Explanation of the Answer
The correct answer to the given question is option 'A', which states that when an SCR is in forward blocking mode, the applied voltage appears across only one junction. This means that the entire applied voltage is dropped across a single junction within the SCR.
Reasoning
To understand why the voltage appears across only one junction, it is important to understand the structure of an SCR.
Structure of an SCR
An SCR is a four-layer, three-junction semiconductor device. The layers are named P1, N1, P2, and N2, starting from the anode side. The three junctions are J1, J2, and J3, as shown below:
J1: P1-N1 Junction
J2: P2-N1 Junction
J3: P2-N2 Junction
Explanation
When the SCR is in forward blocking mode, the anode is at a higher potential compared to the cathode. This causes J1 and J2 to be reverse biased, while J3 is forward biased.
In this mode, the depletion layers at J1 and J2 become wider, preventing the flow of current through these junctions. However, the depletion layer at J3 becomes narrower, allowing the flow of current through it.
Since the entire applied voltage is dropped across J3, the voltage appears across only one junction. This is because the other two junctions, J1 and J2, are reverse biased and do not allow the applied voltage to be dropped across them.
Therefore, in forward blocking mode, the applied voltage appears across only one junction, which is J3.
Conclusion
When an SCR is in forward blocking mode, the applied voltage appears across only one junction, specifically J3. This is because J1 and J2 are reverse biased and do not allow the voltage to be dropped across them.
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