Electric and Magnetic Fields: Magnetic Fields and Forces

Magnetic Fields are generated by moving charges or permanent magnets.
A magnetic field can be depicted visually by magnetic field lines that exit from a magnet’s north pole and enter its South pole. The denser these lines, the stronger the magnetic field.
The magnetic field strength (‘B’) is measured in teslas (T).
The direction of a magnetic field is from the North Pole to the South Pole outside a magnet, and from the South Pole to the North Pole inside a magnet.

Magnetic forces are experienced by a moving charged particle in a magnetic field. This particle experiences a force known as the Lorentz force.
The magnitude of this force is equal to qvBsinθ, where ‘q’ is the charge, ‘v’ is the velocity, ‘B’ is the magnetic field strength, and ‘θ’ is the angle between the direction of motion and the direction of the magnetic field.
The direction of the force on moving charges in a magnetic field is given by Fleming’s left-hand rule.
The magnetic force can change the direction of the moving charged particle but cannot do work on it because the force is always perpendicular to the direction of motion.

Current in a wire creates a magnetic field around it. The right-hand rule gives the direction of this field.
The electromagnetic force is one of the four fundamental forces and it acts between charges. It has two aspects: an electric force (caused by stationary charges) and a magnetic force (caused by moving charges).
Ampère’s law states that the magnetic field produced by an electrical current is proportional to the size of that current with a constant of proportionality equal to the permeability of free space.
Faraday’s law of electromagnetic induction states that a change in magnetic field within a closed loop of wire induces an electromotive force (EMF) in the wire.

Ferromagnetic materials, such as iron, cobalt, and nickel, are strongly attracted to magnetic fields and can be permanently magnetized.
Diamagnetic materials are weakly repelled by magnetic fields.
Paramagnetic materials are weakly attracted to magnetic fields but cannot retain any magnetization in the absence of an externally applied magnetic field.

Magnetic Fields and Forces are used in several everyday applications such as electric motors, speakers, MRI scans, and data storage devices.
Magnetic fields are used in transportation technologies such as Maglev trains.
Electromagnetic induction is used in the generation of electricity in power stations.