Magnetic Field

A magnetic field is created by a moving charge. Practical magnetic fields are created by Electron Current.

But Permanent Magnets are not moving charges, so how is that magnetic field generated??

Through a quantum mechanical property called Electron Spin.

Danger

Magnetic fields are NOT Conservative, because the force on a moving charge depends on the path and velocity, rather than just the initial and final position.

Magnetic interactions are understood in terms of Magnetic Poles: north and south.

Magnetic poles never occur in isolation

All magnets are dipoles, with two poles.

Laws

• BS Law
• Ampere’s Law

For a Solenoid, the magnetic field is given by (see solenoid note for details)

$B=\frac{u_{0}NI}{L}$

Related

• Electric Field
• Magnetic Material
• Magnetic Dipole