A solenoid () is a type of electromagnet formed by a helical coil of wire whose length is substantially greater than its diameter, which generates a controlled magnetic field. The coil can produce a uniform magnetic field in a volume of space when an electric current is passed through it.
André-Marie Ampère coined the term solenoid in 1823, having conceived of the device in 1820.
The helical coil of a solenoid does not necessarily need to revolve around a straight-line axis; for example, William Sturgeon's electromagnet of 1824 consisted of a solenoid bent into a horseshoe shape (similarly to an arc spring).
Solenoids provide magnetic focusing of electrons in vacuums, notably in television camera tubes such as vidicons and image orthicons. Electrons take helical paths within the magnetic field. These solenoids, focus coils, surround nearly the whole length of the tube.

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    Electrical '68 cj5 solenoid(s), Dauntless V6

    I've had Jeep for 6-8 months. It started and ran (not great but was drivable) when I bought it. I'm troubleshooting a no start issue after replacing a old HEI distributor with a new HEI one. I'm not getting enough volts to fire the new HEI. Was originally was at 10.5 volts at startup. I've...
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