Semiconductor Electronics: Materials, Devices and Simple Circuits MCQs for NEET — Physics Questions with Answers

The breakdown voltage of a diode can occur due to either avalanche effect or Zener effect. For breakdown voltages less than approximately 5V, the Zener effect is dominant, while for voltages above 5V, the avalanche effect is more significant. Since the breakdown voltage given here is exactly 5V, it can be due to either effect.

A diode is a nonlinear device. This means that its current-voltage (I-V) relationship is not a straight line, which indicates that it does not follow Ohm's law across its entire operating range. Instead, a diode allows current to flow easily in one direction (forward bias) while offering high resistance in the opposite direction (reverse bias).

For a bridge rectifier, the peak load voltage ( V_{peak} ) is related to the RMS value of the secondary voltage ( V_{rms} ) by the formula: V_{peak} = V_{rms} imes rac{2}{ ext{sqrt}(2)} . Given that V_{peak} = 40V , we can rearrange this formula to find V_{rms} , which yields approximately 28.3V.

$ V_{rms } = { V_m \over \sqrt 2 } $

In a zener diode, the load current remains approximately constant when the source voltage increases. This is because the zener diode regulates the voltage across the load, ensuring that the load current stays stable even if there are fluctuations in the source voltage.

A varactor diode, also known as a varicap or tuning diode, is specifically designed to act as a variable capacitor when reverse biased. The capacitance of a varactor diode changes with the applied reverse voltage, making it ideal for applications like voltage-controlled oscillators and frequency modulators.