Electronics
LED resistor calculator: what resistor for 12 V?
Work out the series resistor for an LED on 12 V, 5 V or any supply. Rounds up to a standard value and shows the current and the resistor's power.
Ohm’s law
Electronics
Make a simple LED circuit on a breadboard (maths included)
Light an LED from a 9 V battery on a breadboard, with a wiring diagram, which way round the LED goes, and the resistor maths worked through step by step.