Class 12 NEET Physics Semiconductor Electronics Part 2

Concept:A diode acts as a closed switch when forward biased and as an open switch when reverse biased.Formula:For an ideal diode: forward bias — zero voltage drop; reverse bias — infinite resistance, so full applied voltage appears across it.Solution:Step 1: The input AC voltage $V_{\text{in}}$ is applied to the series combination of diode $D$ and resistor $R$.Step 2: During the positive half-cycle ($V_{\text{in}} > 0$):Diode is forward biased → conducts → voltage across $D$ is approximately $0$ V.Step 3: During the negative half-cycle ($V_{\text{in}} < 0$):Diode is reverse biased → no current → entire $V_{\text{in}}$ appears across $D$.Step 4: Therefore, the voltage waveform across $D$ is zero during positive half-cycles and equals the negative part of $V_{\text{in}}$ during negative half-cycles.Shortcut:The diode voltage waveform is the inverse of the load voltage waveform — it clips the positive half and passes the negative half unchanged.Answer:The correct option is the waveform that shows zero voltage for the positive half and the full negative sinusoidal swing for the negative half.