Magnetism

• Magnetic Field Strength (B) is the density of the field lines
• The motor effect is when a current carrying wire in a magnetic field produces a force on itself, due to an interaction between its own magnetic field and the other field.
• A cyclotron is a machine comprised of two semi-circular Dees with a small gap between them. A magnetic field is applied perpendicular to the Dees, which causes protons to spiral. A potential difference is applied across the Dees to accelerate protons accross the gap, however this must be reversed every half a cycle to ensure protons continue to travel in the same way. As the velocity of the protons increases, their radius does too.
• Faraday's law states that the magnitude of the induced emf is directly proportional to the rate of change of flux linkage:

  $\epsilon =$$N\frac{\Delta \phi}{\Delta t}$
• Lenz's law states that the direction of the induced current is such that it opposes the change producing it. This is because the emf induced will produce its own magnetic field, which will oppose the initial magnetic field.
• The direction of the induced current is given via fleming's right hand rule
• A transformer consists of a soft iron core with two coils wrapped around each side. An AC input is applied, which due to the primary coil induces a magnetic field in the iron. This carries the current to the secondary coil, which induces an emf. The side with more coils will produce a greater voltage.