Electricity is very rarely visible, but can be seen in the form of lightning. Lightning is a large spark that occurs when many electrons move very quickly to even out an unequal distribution of electrons. Other, smaller sparks can be seen when you scuff your feet across carpet and then touch something like a metal doorknob. Both these types of sparks are the same form of electricity: static electricity. Static electricity is also responsible for a balloon rubbed on your sweater sticking to the wall and for your clothes coming out of the clothes dryer sticking together.
Every object consists of atoms, which have small charged particles. Tightly held, heavier, positively charged particles are called protons, while loosely held, lighter, negatively charged particles are called electrons. When there are excess electrons in an object, it is considered negatively charged; when there is a deficit of electrons, the object is considered positively charged. Charged objects exert a force on each other, which can be calculated based on the objects’ charges and distance from each other using Coulomb’s law. Some materials transmit electrons easily and are called conductors, while other materials, called insulators, restrict the transmission of electrons.