Unit: Energy and Control- Electricity

 Electricity was first observes over 2000 years ago by Thales of Miletus, a Greek scientist. When he rubbed a piece of amber (a natural glass like substance) with fur or cloth, he notices that it attracted small objects such as feathers and hairs. We now know that this is static electricity. But scientists didn’t understand electricity until the 1700’s. And inventors didn’t make useful electrical devices until the late 1800’s.

 In any electrical circuit, the electricity must flow along a complete path, called a circuit, in order to work. For example, electricity flows from a battery, through a light bulb, and back into the battery-a complete loop.  Look closely at a clear light bulb. The tiny piece of metal is called the filament. The filament is a type of metal called tungsten that does not wear out too quickly. When an electric current passes through the filament, the tungsten heats up and glows. More electrical energy makes the filament become brighter. But too much voltage can heat the filament too much and it can break.

 In a series circuit, the electricity can flow along one path only. For example, electricity flows from a flashlight battery, through wires to the filament of a bulb, and back into the battery. If you add two more bulbs or two more batteries there is still only one path for the electricity to follow. If you break the path anywhere, say by removing a bulb, the entire circuit fails. Remove one bulb from the circuit and all the bulbs go out. Some strings of lights are connected this way. When one light foes out, they all go out. Finding the broken one can be difficult.

 Think of a parallel circuit as being like your route to and from school. If you can follow several paths or roads, then it is like a parallel circuit. If one path is blocked, you can follow another.  Two or more light bulbs connected in a parallel circuit are brighter than two or more light bulbs connected in a series circuit. This is because, in a parallel circuit, each bulb is connected by its own path to and from the battery, so each bulb gets the whole amount of power from the battery. In a series circuit, the electrical energy is shared with all the other bulbs. If you remove one bulb from a parallel circuit, all the other bulbs remain lit. For this reason, electric wiring in your home is connected in parallel circuits.

 Voltage is the amount of energy in a circuit. You can increase the voltage in a circuit by using two batteries connected in series. When the positive end of a 1.5-volt battery touched the negative end of another 1.5-volt battery, the power in the circuit increased from 1.5-volts to 3.0-volts. If a third battery is added, the power is increased again to 4.5 volts and so on. The bulb glows brighter and brighter when batteries are connected this way.

 Bill Nye the Science Guy- Season 1: Electricity.  E9sA