What voltage is typically used to cause an LED to light?

The typical voltage used to cause an LED (Light Emitting Diode) to light is around 2 to 3 volts for most standard LEDs, making 3 V DC the most suitable choice among the options provided. LEDs require a specific forward voltage, which is the minimum voltage that must be applied in the forward direction for the LED to conduct electricity and emit light.

Standard red, green, and yellow LEDs often have a forward voltage of about 2V to 2.5V, while blue and white LEDs might require around 3V to 3.5V. Therefore, using a 3 V DC supply provides sufficient voltage to ensure that the LED will illuminate reliably without being damaged due to overvoltage.

When considering the other options, 1 V AC is too low to forward-bias the LED, and AC voltage could damage the LED as it could reverse bias it, leading to potential failure. A supply of 5 V AC would also be unsuitable, as it exceeds the forward voltage required for typical LEDs and could likewise lead to damage. Lastly, while 9 V DC could potentially illuminate an LED, it exceeds the forward voltage limit and risks burning out the LED unless a resistor is placed in series to limit