Magnetism and Electromagnetism

Basic Concepts and Definitions

A magnet is an object that produces a magnetic field, attracting or repelling other objects made of certain materials like iron.
The magnetic field is a region around a magnetic material or a moving electric charge within which the force of magnetism acts.
Magnetic poles are the two ends of a magnet, labeled North and South, where the magnetic field lines emerge and converge, respectively.
Unlike poles attract each other (North-South) while like poles repel each other (North-North or South-South).

Field lines always go from the North to the South pole of a magnet. They never cross and are denser where the magnetic field is stronger.
Iron filings can be used to visualise these field lines.

When an electric current passes through a wire, it creates a magnetic field around it. This is the principle behind electromagnetism.
The right-hand grip rule can be used to determine the direction of the magnetic field. If you curl your right hand around the wire with your thumb pointing in the direction of the conventional current, your fingers will wrap around the wire in the direction of the field.

A solenoid is a coil of wire which produces a strong magnetic field when current passes through it.
An electromagnet is essentially a solenoid often wrapped around an iron core, which significantly increases the strength of the magnetic field.
The strength of the magnetic field can be adjusted by changing the number of coils, the current, or the material of the core.

The motor effect refers to a force experienced by a current-carrying wire in a magnetic field. The principle behind this is known as Fleming’s left-hand rule.
Fleming’s left-hand rule can predict the direction of the force, magnetic field, and current. Extend your thumb, index finger, and middle finger of your left hand such that they are perpendicular to each other. Your thumb points to the direction of motion (Force), your index finger to the direction of magnetic Field, and your middle finger to the direction of Current.

Electromagnetic induction is the process of generating an electromotive force (EMF) by moving a conductor in a magnetic field or changing the magnetic field around a stationary conductor.
Faraday’s law of electromagnetic induction states that the induced EMF in a circuit is directly proportional to the rate of change of magnetic flux through the circuit.
Lenz’s law states that the induced EMF will always work to oppose the change in magnetic flux that produced it, maintaining the conservation of energy.