Hobbies And Interests
A Penny as Electrical Conductor
Pennies used to be made primarily of copper, which is an excellent electrical conductor, but modern pennies are 98 percent zinc, which has only 27 percent the conductivity of copper. The amount of electricity a conductor will allow to pass, however, is also a function of cross-sectional area, and the cross-sectional area of a penny is large enough to more than compensate for the lower conductivity of zinc. Consequently, a penny will pass thousands of amps of electricity, and in the event of a large current surge, the wires in the circuit would melt before the penny did.
The Function of a Fuse
A typical fuse consists of a thin wire or piece of metal with a low melting point, and it's designed to burn out quickly in the event of a power surge. When it blows, it disconnects any devices on the circuit, thereby protecting them from the surge. If a fuse blows frequently in a particular circuit, it's usually an indication that something is wrong with the circuit, such as a bad connection that is producing a short circuit. If you attempt to restore functionality by installing a fuse with a higher rating, you're potentially exposing your equipment to a higher current that could ruin it.
Electrocution and Fire Danger
Another characteristic of fuses not shared by pennies is the presence of electrical insulation. The conductor in a fuse is usually protected by a layer of plastic or glass to protect the unwary person who happens to touch one while electricity is flowing. A penny has no such insulation, so not only can it deliver a serious shock, it can also start fires. If a large enough current passes through one, electricity can arc from the penny to any nearby metal surface, such as the cover of the fuse box. The high heat produced by arcing can ignite any flammable materials in the vicinity.
Better Alternatives
If you need to replace a fuse quickly, and you don't happen to have a replacement handy, almost anything is safer for you and your house than a penny. The only thing that is safe for your equipment, however, is a fuse with the same or a lower rating. If this is the first time the fuse has blown, the anomaly that caused it to blow may not recur, and a fuse with a lower rating may hold until you can buy a proper replacement. Using a fuse with a higher rating exposes your equipment to damage. If the fuse blows frequently, it's a sign that the circuit, or a device on it, needs repair.