3. Resistor Selection
Question.5
You’re powering a high-power white LED with a forward voltage of 3.3V and a desired current of 60mA, using a 9V DC power supply.
You calculate the resistor value using Ohm’s Law:
R = (9V − 3.3V) / 60mA = 95Ω
You choose a 100Ω resistor rated at 1/4W (0.25W) as the closest available value.
After a short duration, the resistor becomes hot and visibly burned on the board.
What is the most likely reason?
