Summary
Highlights
Introduction to magnetic fields. Magnetic fields are bipolar, possessing a north and south pole which cannot be isolated. They are vectors, requiring vector addition for net field calculations.
Discussion of magnetic poles, where opposite poles attract and like poles repel. Earth behaves like a bar magnet, with its magnetic north being a magnetic south pole.
Explanation of magnetic field lines, which conventionally exit the north pole and enter the south pole. This applies to both bar magnets and solenoids (electromagnetic coils).
Electric current and magnetic fields. Moving electrons generate magnetic fields. A wire carrying current has a magnetic field that can be detected with a compass.
Introduction of the first right hand rule: wrapping your hand around a wire with your thumb pointing in the direction of conventional current indicates the direction of the magnetic field with your fingers. Also covers the right-hand rule for solenoids.
A charge moving parallel to a magnetic field experiences no force. Force is exerted only at an angle to the field, and this force is calculated using F = qvBsinθ.
The FBI (Force, B-field, I-current) right-hand rule for determining the direction of force on a positive charge moving in a magnetic field. If it is a negative charge, reverse the force direction.
A wire carrying current in a magnetic field experiences a force, given by F = ILBsinθ, where θ is the angle between the wire and the magnetic field.
When particles enter a magnetic field at a velocity they take a curved path due to the force exerted on them. The work done on the charged particle is zero because of the angle at which the particle enters the field, which makes the displacement zero.
Parallel currents exert an attractive force on each other; anti-parallel currents exert a repulsive force. Conventions for representing current direction (into the page vs. out of the page) is covered.
A photo shows the earth's magnetic field, distorted by electromagnetic radiation from the sun.