http://micro.magnet.fsu.edu/electromag/java/index.html
The site has a variety of interactive java simulations for many of the
topics in O and A level physics. It also has a lot of notes.

• Variable capacitor
• How a transformer works.
• RC circuit and charging a capacitor.
• How a loud speaker works.
• Rutherford’s Experiment.
• Tuning a radio receiver.
• Ohm’s Law
• The DC generator
• The AC generator
• Faraday’s Electromagnetic experiment
• Factors that determine capacitance