This course will look at Electric and Magnetic interactions only. Electric forces originate with electric charges , and magnetic forces emerge from the movement of electric charges. Normally, objects have a balance of positive and negative charge, but some types of material can support a charge separation.
Charge flows easily through conductors so it is difficult to keep the charges separate.
Conductors are materials that have lots of charges that are relatively free to move around within the material. Semiconductors are useful because their carrier density can be changed drastically by adding impurities, or changing the temperature, or the incident light, etc. Electric charge separation Charges are transferred on or off insulators by physical contact. When some insulators are rubbed together friction can transfer charge from one insulator to the other. The charges will stick at the places where they were separated to or from.