Bulbs and switches

Today two patterns based on electrical symbols to represent applications of tungsten (left) and ruthenium (right).

Tungsten has the highest melting point of all metals. It was used extensively in the filaments of incandescent light bulbs throughout the 20th century and so I have based my pattern on a electrical symbol for an incandescent bulb. Bulbs with tungsten filaments were introduced to the market in 1904, by Hungarian company Tungsram. Their bulbs gave brighter light and lasted longer than those of Swan and Edison which had carbon filaments. As only 5% of the electrical energy used in running an incandescent bulb is dissipated as light (the rest is lost to the surroundings as heat), after 100 years of use these bulbs have largely been phased out in recent times, in favour of more energy-efficient alternatives.

As noted in the post on vanadium, tungsten also has a Scandinavian name (meaning heavy stone) despite being discovered by two Spaniards, Juan and Fausto Elhuyar. Though they isolated the metal in 1783, the name was not officially settled until 2005. Until then, wolfram, from which tungsten takes its symbol W, was accepted by IUPAC as an alternative.

Ruthenium is a hard, inert metal discovered in 1844 and mainly used in electrical applications. It found particular use in the reed switches used in British telephone exchanges in the 1970s and 1980s. Reed switches are electrical switches operated by a magnetic field. They consist of a pair of flexible ferromagnetic ‘reeds’ in a hermetically sealed glass capsule. Applying the magnetic field causes the reeds to attract each other and complete an electrical circuit, springing apart again when the magnetic field is removed. A thin layer of a metal such as ruthenium which is resistant to wear and has a high melting point is used on the contact area of the reeds.

To evoke the era of 1980s British Telecom, here is a picture of my “Make Buzby Happy” badge – being the child of a BT engineer, a highlight of my childhood was meeting the mascot Buzby in ‘person’. In these Covid times this is perhaps a good message to promote – that a phonecall can lift someone’s spirits.

With thanks to Mark Main for suggesting the ruthenium reed switch.

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