Electronics bench

Step 1 of 8

Close the circuit

Why nothing happens until the loop is complete

Electricity does not get used up at the LED. It leaves the supply at +, travels all the way round, and comes back in at −. If any part of that path is missing, nothing moves anywhere — not even in the part that is connected.

The supply, a resistor and an LED are already on the bench, and most of the wiring is done. One join is missing.

Your task: Tap a terminal, then tap another, to join them and close the loop.

Supply+−220Ωred LED+−
One leg of Supply is not joined to anything. Current has to leave the supply, go all the way round, and come back — a loose end stops it.