Electricity is very rarely visible, but it 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 a metal doorknob. Both these sparks represent the same form of electricity: static electricity. Static electricity is also responsible for allowing a balloon that you rubbed on your sweater to cling to a wall and for causing your clothes to come out of the dryer stuck together.
Matter is made up of atoms, which consist of small, charged particles. The tightly held, heavier, positively charged particles are called protons, while the loosely held, lighter, negatively charged particles are called electrons. When there are excess electrons in an object, it is considered to be 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.