How Electricity Works — Current, Voltage and Resistance Explained

Electricity powers nearly everything in modern life, yet most people have only a vague sense of how it works. The three fundamental concepts — voltage, current and resistance — can be understood intuitively with the right analogy, and from there, everything else follows.

The Water Pipe Analogy

The most effective way to understand electricity is to think of water flowing through pipes:

• Voltage is like water pressure — the force that drives flow. High voltage = high pressure.
• Current is like the flow rate — how much water (charge) moves per second. Measured in amperes (amps).
• Resistance is like a narrow pipe — it restricts flow. Measured in ohms.

What Is Electric Current?

Electric current is the flow of electric charge — specifically, the movement of electrons through a conductor. In a metal wire, free electrons (outer-shell electrons not tightly bound to any atom) drift through the material when voltage is applied. One ampere means approximately 6.24 × 10¹⁸ electrons passing a point per second.

What Is Voltage?

Voltage (or electromotive force) is the difference in electric potential between two points — the "pressure" that drives electrons to flow. A 9V battery has 9 volts of potential difference between its terminals. UK mains electricity is 230V; US mains is 120V. Higher voltage can push more current through the same resistance.

What Is Resistance?

All materials resist the flow of electrons to some degree. Conductors (copper, silver, gold) have very low resistance. Insulators (rubber, plastic, glass) have very high resistance. Resistors are components deliberately designed to limit current flow in a circuit.

Resistance increases with temperature in most metals — why light bulb filaments have high resistance: they're designed to glow white-hot, which only happens because their resistance is high enough to convert electrical energy into heat and light efficiently.

Ohm's Law — The Relationship

George Ohm formalised the relationship in 1827:

V = I × R    (Voltage = Current × Resistance)

Double the voltage with the same resistance, you get double the current. Double the resistance with the same voltage, you get half the current. This simple relationship governs the behaviour of almost all simple electrical circuits.

AC vs DC

Direct current (DC) flows in one direction — batteries produce DC. Alternating current (AC) reverses direction at a set frequency — mains electricity in most countries alternates at 50Hz (50 times per second) or 60Hz. AC is used for mains power because it can be transformed to very high voltages for efficient long-distance transmission, then stepped back down for home use.