Physics Speedrun - Magnetic Field
Magnetism is the interaction of clectric currents or moving charges. Magnetic field is
- Created by / interacts on currents or moving charges
- Closed field lines without beginning or end
Ampere Force
Magnetic field exerts a force on a current, called Ampere forece. In uniform field:
The magnetic field
General case: nonuniform
In uniform field, it is equivalant to a stright wire from A to B.
Magnetic field freated by current
Magnetic Dipole
Total force is zero, but torque on the loop:
Magnetic dipole moment:
Direction of
is defined by the right-hand rule.
Torque:
Valid for any plane current loop. A small circular current is called a magnetic dipole.
For a
Orbital angular momentum:
Lorentz Force
Magnetic field exerts a force on a moving charge:
Lorentz force does not do work on the charge.
When
When
The charge moves in a helix.
Lorentz equation: Total force on a charge in electromagnet field
Source of Magnetic Field
Biot-Savart Law
Magnetic equivalant to Coulumb's law. Magnetic field due to an infinitesimal current:
Permeability of free space:
Direction: right-hand rule.
Total magnetic field due to a full current:
Infinite straight current:
Magnetic dipole moment:
Gauss's Law for Magnetic Field
Magnetic flux:
Gauss's law for magnetic field:
Magnetic field lines are closed lines without beginning or end.
Ampere's Law
Magnetic field is produced by all currents:
Magnetic field is not a conservative field:
Maxwell equations for steady magnetic field and electrostatic field:
No magnetic field when
Uniform magnetic field inside: Follow the intergration path.
Nonuniform field inside: