Nernst lamp

A Nernst lamp is an early type of electric light that uses a special, temperature-sensitive material called a thermionic emission wire, usually made of carbon or metal. When electric current passes through the wire, it heats up and emits light due to thermionic emission—the release of electrons. To enhance brightness, a small amount of gas, like neon or argon, is enclosed around the wire, which glows when excited by the current. The lamp produces a steady, warm light, and was an important step in developing practical electric lighting before modern incandescent and fluorescent lamps became common.