Electromagnetic interactions
Interaction between a current-carrying wire and permanent magnets
Interaction between two current carrying wires
- the source of the force on each wire is the magnetic field produced by the other
- parallel wires attract if current directions are the same, and repel if current directions are opposite
- this effect is used to define the unit of current ( Ampere) in the metric system: consider two long parallel wires separated by 1m distance and carrying the same current. If the force between these wires is 2 x 10-7 N on each meter of wire, the current is defined as 1 Ampere.
- strength of the magnetic field, units in T (Tesla) or G (gauss)
the strength of the magnetic field at a distance of 1m from
a long straight wire carrying a current of 1A is 2 x 10-7 T.
Interaction between magnetic field and moving charged particles
magnetic field interacts only with moving charged particles
force: depends on the velocity of the particle (v), intensity of`
the magnetic field field (B), charge of the particle (q), and
angle (?) between field and velocity:
direction: perpendicular on the plane formed by v and B