 Solenoid

Solenoids are a type of electromagnet coil of helical shape.

Solenoid means "tubular" in Greek.

Solenoids are simpler to build as they don't require insulated wire as in modern electrical cable because as the electromagnetic coils don't touch one another.

As such it is perhaps the reason why some early electromagnetism experiments were carried out with solenoids, which André-Marie Ampère named in 1823.

But the downside of this is that the magnetic field they can generate is less strong.