Voltage, Current & Resistance

The three quantities every other lesson builds on.

Voltage (V), measured in volts, is the electrical pressure pushing electrons through a circuit — the difference in electric potential between two points. Think of it as water pressure in a pipe.

Current (I), measured in amperes (amps), is the rate electrons actually flow past a point. Same water analogy: it's the flow rate, in litres per second.

Resistance (R), measured in ohms (Ω), is how much a material opposes that flow. A narrow pipe resists water flow more than a wide one; a thin wire resists current more than a thick one.