Magnetism
Electrostatic forces operate on charges regardless of their motion. Magnetic forces only operate on moving charges. This tutorial therefore concentrates on charges in motion.
- The motion of charges gives rise to electric current. The first topic explores the relationship between electric current, charge and the speed at which the charges drift.
- Ohm's law give a relationship between the electric field accelerating the charges and the steady-state electric current that flows in response to this. Origins of resistance are examined and quantities such as resistivity, conductivity and ionic mobility are defined.
- Magnetic fields are detected through their action on charges in motion. The magnetic force is analysed, mainly with reference to its applications in mass spectrometry and the Hall effect.
- Magnetic fields are induced by charges in motion. This topic introduces the Biot-Savart law, which enables us to calculate this magnetic field, and applies the law to charges travelling in a straight line and in a circle, with particular application to a Bohr orbit. Orbital and spin magnetic moments are discussed.
- Electromagnetic radiation is an oscillation of electric and magnetic fields. The theory of this is beyond the scope of this course, but some important results are summarised, which have particular application in quantum mechanics.
In each tutorial the level of difficulty of each topic is colour-coded.
This is intended to give you some idea of when it might be appropriate to have a go at it. The colour codings are intended to mean:
Level 0 (green)- this is basic material that you have probably encountered already, although the approach may be slightly different. No prior knowledge is assumed.
Level 1 (gold) - this material has some prerequisites that are covered in the first year mathematics for chemists course. It will be made clear what these prerequisites are; many students will have covered them already as part of Physics or Further Mathematics.
Level 2 (red) - this material is more advanced. It has been provided as background to help you understand courses in the second and third years. You may not be in a position to understand this until you have completed and digested the first year.