Static Electricity
Unlike current electricity that moves, static electricity stays in one place. It is the build up electric charges on an object. These charges are called static charges because they are stationary. The static charges can be positive or negative . When two substances are rubbed together, electrons are pulled over from the material that has the weaker attraction and attach to the material that has the stronger attraction. This causes both materials to become charged . The material losing electrons become positively charged and the material gaining electrons become negatively charged. Electric charges follow certain rules and one rule states that unlike charges are attracted to each other. When the charge on one object is great enough between the two objects the second object is also charged. This creates a path for the electrons to travel. Static discharge is the end result. The discharge can be very slow and quiet or quick causing a spark of light and sound. This is the theory of how lightning and thunder is created on a larger scale.( Ardley,118)
Benjamin Franklin proved that static discharge and lightning were the same thing. He tied an iron spike to a still kite and flew it during a thunderstorm. When lightning hit the rod it cause a spark. Although he proved his theory, it was a very dangerous thing to do. He also invented the lightning rod from the results of this experiment. (Rawsthorne,1)
Current Electricity
The path in electric current takes as it flows is called a circuit. The electric current that flows from a battery always travels in the same direction. This type of current is called direct current (DC). The electric current in battery is produced by chemicals. Inside the battery are two metal parts that are covered in chemicals. When the battery is connected to an appliance the chemical inside the battery reacts to each other, and produce charged particles. Negative charge collects on one end and positive collects on the others.
( Ardley,132)
Alessandro Volta was the creator of batteries. Another scientist, Lugi Galvani thought that animal electricity caused a dead frog's leg to jump when it was touched with a steel knife. Volta realized that the two different metals, the steel knife and the tin tray that the frog was lying on was the cause of the movement in the frog's leg. He showed that when moisture comes between two different metals, electricity is created. This led to the widely used battery of today. Volta showed that electricity could travel through wire from place to place. Voltage is the energy that moves electrical charges between two parts through a wire. It gets its name from Volta.(Rawsthorne,1-2)
But most of the electricity we use comes from the supply lines from the power station. This current is constantly changing directions backward and forward. It changes directions as often as 50 - 60 times per second. (Ardley,122) It is called alternating current (AC). AC is used for the main supply because it can be transmitted more cheaply than DC , for most purposes AC is more efficient. When two identical objects are powered separately one by AC and the other by DC such as a light bulb or radio you can not see or hear the difference.
Conductors and Insulators
Electricity flows through some materials easily. These materials are called conductors. Metals are good conductors of electricity. But electricity can not flow through all materials. These materials that electricity can not flow through are called insulators. Both types of materials serve a very good but different purpose in the travel of electricity.
All metals conduct electricity. Silver is the best, which is used in circuits in computers, but expensive. The best least expensive metal is copper. Power lines use copper wires to supply us with electricity. Water is a weak conductor but you can still get a shock if you touch and electric appliance with wet hands. Insulators are used to prevent electricity from flowing where it is not wanted. Wires in the appliances we use are insulated to protect them and us from live wire with plastic coating. Plugs and sockets are usually made form plastic or rubber to make them safe to touch. Ceramic is not as flexible rubber or plastic but is an excellent insulator because; it can withstand high temperatures. It is used to coat electric ovens.(Ardley,125)
Electric charges are measured in the metric unit of coulombs; thus the flow rate of a current is measured in coulombs per second. The amount of current flowing through a conductor is usually expressed in amperes, which is equal to one coulomb per second. ( VanCleave,34)