Which of the following statements about diode is correct?

Analyze the question: We need the true statement about a diode (a p-n junction) under forward and reverse bias.

Concept: A diode is made by joining p-type and n-type semiconductors. It conducts easily in one direction only.

• Forward bias (p-side connected to the positive terminal, n-side to the negative): the depletion layer becomes narrow, so the diode has low resistance and a large current flows once the threshold voltage is passed (about 0.6 V for silicon).
• Reverse bias (p-side to negative, n-side to positive): the depletion layer widens, so the diode has very high resistance and only a tiny leakage current flows.

Checking each option:

• A. Reverse bias diodes have low resistance. False. Reverse bias gives high resistance.
• B. Forward bias diodes have high resistance. False. Forward bias gives low resistance.
• C. Forward bias diodes produce high current. True. Low resistance means a relatively large current flows.
• D. Forward bias diodes function as a result of heat. False. A diode works because of the applied voltage and the movement of charge carriers across the junction, not because of heat.

Exam tip: Remember "Forward = Free flow." Forward bias means low resistance and high current. Reverse bias means high resistance and almost no current. Many WASSCE and JAMB diode questions rely on this idea.