It was found as early as the 17th century that if amber was rubbed, small particles would be attracted to it. This phenomena is widely know today as static electricity. If you rub a balloon on your jumper, it becomes charged with respect to you or a wall for example. It is thus attracted towards the wall or you.
Investigate the effect of applying different charges to the plates in the applet below:
You may remember from school that "Like charges repel" and "Unlike charges attract". An every day example of this is the force that can be experienced when experimenting with magnets. The same principle applies to the concept of electrical charge. A negatively charged particle will be repelled from another negatively charged particle but attracted towards a positively charged one. It is possible to supply a charge to metal plates. The Java Applet above demonstrates this principle. If you supply a positive charge to the left hand plate (by clicking once on the left - up arrow) you will see that the negatively charged particle moves towards that plate. (Unlike charges attract.)
Conversely, if you apply a positive charge to the right hand plate, the negatively charged particle will move towards the right hand plate. - Applying a negative charge to either plate will cause the particle to move away from that plate. If both plates are supplied with an equal charge, the particle will find equilibrium in the middle.
