what is a solenoid and how can its the polarity be controled?

Question

for the defintion of solenoid write it as simple as possible, have a diagram or a site that explain everything through videos. Please and thank you

Answer 1

A solenoid is a coil of wire which becomes an electromagnet when current is passed through it. The coil can--but does not have to--surround a metal core. The polarity is controlled by the direction of current flow. My second reference has some good diagrams.

Answer 2

Technically a solenoid is just a coil of wire.

More commonly it is used to decribe a coil of wire with a current running through it. When the current runs through the wire the electromagnetic flux lines (which run perpendicularly to the direction of current) run together through the coil in one direction and outside the coil in the other direction.

THe polarity of the electromagneitsm is simply controlled by the direction in which the current it running.
Use the right hand rule - make a thumbs up with your right hand. Imagine the current running up your thumbs. Then the direction of your curled fingers is the flow of flux around your thumb/wire.

The rest follows.