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QPages 352-354: Q11: HC Verma: Concepts of Physics - Volume 2 Electric Current through Gases Pages 352-354: Q11 Solution: The plate current in a diode is 20 mA when the plate voltage is …

⚠️ Common Exam Traps & Conceptual Pitfalls

Students often treat the diode like a resistor and expect the plate current to keep increasing with voltage; they overlook that once the emission (saturation) voltage is reached, the current is limited by the cathode emission and stays constant. If the same current appears at two successive voltages, the diode is already in saturation, so the same value applies at any higher voltage.

The plate current in a diode is 20 mA when the plate voltage is 50 V or 60 V. What will be the current if the plate voltage is 70 V?

Step-by-Step Verified Solution

**Answer:** The current is 20 mA. **Step-by-Step Explanation:** The plate current is 20 mA at both 50 V and 60 V, which indicates that 20 mA is the saturation current. For a given temperature, the saturation current remains constant for all voltages above the saturation voltage. Hence, at 70 V, the current is still 20 mA .

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