1. Magnetism
Magnetism originates at the atomic level and is caused by moving electric charge
Magnetic objects:
Create magnetic fields around themselves
Exert magnetic forces on other magnets, ferromagnetic materials, moving electric charges
Electric fields and forces are created by static (non-moving) electric charges
Magnetism and electrostatics are two sides of same coin – electromagnetism

2. Magnetic Materials Ferromagnetic materials have magnetic domains
Magnetic domains are microscopic regions within a material in which the magnetic fields of individual atoms are aligned
In a non-magnetic object, the domains are randomly aligned, cancelling each other out
In a permanent magnet, the domains are uniformly aligned, reinforcing each other
In “soft” magnetic materials, domains can be temporarily realigned by an external magnetic field

3. Magnetic Domains

4. Magnetic Fields and Forces
As with electric fields, magnetic fields have a direction and depend on distance
Magnetic field lines are drawn as arrows that go
out of the North Pole of a magnet and
into the South Pole of a magnet
closer spacing = stronger field
As with electric forces, magnetic forces are both attractive and repulsive
Unlike magnetic poles (N & S) attract
Like magnetic poles (N & N or S & S) repel

5. Magnetic Field Lines

6. Electromagnetism
Electromagnetism is the magnetism that results from an electric current moving through a wire
The direction of the current determines the direction of the magnetic field
The direction of a magnetic field around a current-carrying wire is given by a right-hand rule
Thumb points in the direction of current
Fingers point in the direction of magnetic field

7. Electromagnetism

8. Force on a Wire with Current
If a current-carrying wire is placed in a magnetic field, a force is exerted on the wire
The direction of force is perpendicular to both the direction of the current and the direction of the magnetic field
The three directions are given by another right-hand rule
Thumb = direction of current
Fingers = direction of magnetic field
Open palm = direction of force

9. Force on a Wire with Current

10. Solenoids and Electromagnets
Solenoids are coils of current-carrying wire that exert a magnetic field
The strength of the field depends on the number of loops in the coil and the amount of the current
Electromagnets are solenoids with a core of ferromagnetic material
The magnetic field from the coil aligns the domains in the core, further strengthening the magnetic field

11. Solenoids

12. Electromagnets