Current Uses
Though used commonly in the past, knife switches are now rare, finding use largely in science experiments where the position of the switch may be plainly seen in demonstration. The knife switch is extremely simple in construction and use, but its exposed metal parts present a great risk of electrocution, and the switch is subject to arcing when opened at higher voltages, which poses a further risk of shock or burns to the operator and can cause fires or explosions under certain conditions.
Open knife switches were supplanted by safety switches with current carrying contacts inside a metal enclosure which can only be opened by switching off the power. In modern applications, automatic switches (such as contactors or relays), and manual switches such as circuit breakers are used. These devices use a snap action mechanism which opens the switch contacts rapidly, and feature an arc chute where the arc caused by opening the switch is quenched. These devices also prevent injury due to accidental contact, as all of the current carrying metal parts of the switch are hidden within or surrounded by insulating guards.
Read more about this topic: Knife Switch
Famous quotes containing the word current:
“The current flows fast and furious. It issues in a spate of words from the loudspeakers and the politicians. Every day they tell us that we are a free people fighting to defend freedom. That is the current that has whirled the young airman up into the sky and keeps him circulating there among the clouds. Down here, with a roof to cover us and a gasmask handy, it is our business to puncture gasbags and discover the seeds of truth.”
—Virginia Woolf (1882–1941)
“I perceived that to express those impressions, to write that essential book, which is the only true one, a great writer does not, in the current meaning of the word, invent it, but, since it exists already in each one of us, interprets it. The duty and the task of a writer are those of an interpreter.”
—Marcel Proust (1871–1922)