Electromagnets

• Electromagnetism is the phenomenon where electric currents produce their own magnetic fields.
• In ordinary wires, coils, solenoids, and electromagnets, electric currents produce their own magnetic fields.
• The magnetic field produced by a current in a wire is represented by field lines, which can be concentric circles around the wire, closest together near to the wire as that's where the magnetic field is strongest.
• The direction of the magnetic field in a wire depends on the direction of the current, which can be remembered using the right hand rule.
• If the current in a wire is going upwards, the magnetic field would be going anti-clockwise and marked with arrows on the concentric circles.
• If the current in a wire is going in the opposite direction, the magnetic field would be going clockwise and marked with arrows on the concentric circles.
• When the magnetic fields of two sides of a coil interact, they will stretch out and form ellipses, and combine to form a single magnetic field which runs straight through the center of the coil.
• A solenoid is a coil with a long piece of wire next to each other, and the magnetic field within a solenoid is strong and uniform outside the coil.
• The north pole of a magnet is where the field lines come out, and the south pole is where they point in.
• Electromagnets are only magnetic for as long as the current is flowing through the wire, and when the current is turned off, the magnetic field disappears and when it's turned back on, it comes back.
• The strength of an electromagnet can be increased by increasing the current that flows through the solenoid, increasing the number of turns in the coil while keeping the length of the solenoid the same, decreasing the length of the coil while keeping the number of turns the same, or adding an iron core to the inside of the solenoid.
• An iron core added to the inside of a solenoid becomes an induced magnet when the solenoid is switched on, massively increasing the strength of the electromagnet's magnetic field but also losing its magnetic field as soon as the current is turned off.