Anyone who has traveled to the United Kingdom has probably marveled at the imperial bulk of the standard U.K. wall plug. With three chunky, rectangular pins, the design at first glance seems almost ridiculously inefficient, especially compared to the svelte footprints of the U.S. and European wall plugs, which manage to get juice to your electronics in under half the space.
But first impressions can be deceiving. In fact, as Tom Scott explains in a new video, the U.K. wall plug is a design classic that is substantially safer than any other plug design on Earth.
The main thing to know about the U.K. wall plug is that while it is bulkier than other designs, every ounce of that additional bulk makes the design safer. This is accomplished in four main ways:
• Prong Design: Like standard U.S. grounded plugs, the U.K. wall plug has three prongs. But the design of these prongs makes it nearly impossible for you to shock yourself accidentally. Unlike in U.S. plugs, half of each prong is coated in insulation. Because of this, even if a plug is not fully inserted into a socket, touching the exposed part of the prongs can’t give you a shock.
• Socket Design: Any kid with a fork or a screwdriver can light his hair on fire in the United States by jamming it into a wall socket. Not so in England, where it would take at least two screwdrivers to manage the same calamitous trick. The U.K. plug is designed so that the grounding prong is slightly longer than the prongs responsible for transferring current. Like a tumbler in a lock, this grounding prong is responsible for “unlocking” the socket, giving access to the more dangerous live and neutral terminals.
• Built-In Fuses: During World War II, a copper shortage resulted in the British government putting fuses into every plug, instead of wiring them directly. Although the built-in fuse adds bulk to the U.K. plug design, it’s also safer: In case of an unexpected electrical surge, the fuse simply blows and the electricity shuts off, preventing fires, electrocutions, and other accidents. It also makes U.K. plugs easier to fix.
• Circuit Design: Finally, there’s the wiring inside the plug itself. Not only is it extremely intuitive, but it has been thoughtfully designed so that if the plug is tugged and the wiring frays, the live and neutral wires are the first to become disconnected, while the grounding wires–the ones responsible for preventing human electrocution when they come in contact with a circuit–are the last to fray.
It’s a truly brilliant design. The only caveat is that, as with Lego, the rugged, bottom-heavy design of a U.K. plug makes it an almost scientifically perfect caltrop.