What is a circuit?
6 min read
A circuit is a closed loop that electricity can travel around. If the loop is broken anywhere, nothing works. That is all a switch does: it opens and closes the loop.
Think of water in a pipe
Voltage (V)The push. Like water pressure from a tank on the roof.
Current (A)How much flows. Like litres per second through the pipe.
Resistance (Ω)What slows it down. Like a narrow pipe.
Ohm's law
V = I × R
If you know any two, you can find the third. A 5 V supply across a 250 Ω resistor gives 5 ÷ 250 = 0.02 A, which is 20 mA.
Every project has the same three parts
- Power: a USB cable, an adapter or a battery.
- Path: wires, with a GND wire bringing current back.
- Load: the thing doing work, like an LED, motor or sensor.
In our wiring videos, red wires are power (5V), black wires are GND, and coloured wires carry signals.
Quick quiz
1. Which wire colour do we use for GND in our videos?
2. 5 V across 250 Ω. What current flows?
Score: 0 / 2