LED Behavior in AC Circuit

Steps:

• AC supply at 2 Hz completes 2 full cycles per second, each with a positive and negative half-cycle.
• LED acts as a diode, conducting current only during the positive half-cycle when forward-biased.
• In each cycle, LED lights once (positive half) and stays off during negative half.
• Thus, LED flashes on/off twice per second, matching 2 cycles.

Why B is correct:

• Diodes like LEDs conduct unidirectionally per diode law, lighting only on positive half-cycles of 2 Hz AC (2 positives/second).

Why the others are wrong:

• A: Incorrect; LED lights twice per second, not once.
• C: Overcounts; only 2 positives per second, not 4.
• D: False; negative half-cycles reverse-bias LED, turning it off.

Final answer: B