Electrical  Circuits


What are Circuits?

Circuits are a closed path for electricity. Every electrical appliance in your home, whether it is battery operated or you plug it in, is a circuit.

How Do Circuits Work?

                 Circuits work because of moving electrons (negitively charged part of atoms). In a cell (battery) the electrons are repelled away from the negative terminal, through the conducting path and the appliance and back to the cell. After going through the path the electrons are attracted to the positive terminal of the power source and ready to go again. 

                The electrons need a complete path or circuit to flow through so the electrons can go from the negitive to the positive terminals of the power source. This flow of electrons is known as an electric current.

If there is a break in the circuit, the electrons can't get through to the appliance and there will be no electrical charge.

Parts of Circuits

All circuits have 3 main parts: a power source, a conducting path and a load (something that will use the electricity). In the labs we did in class we usually used a battery as a power source, a piece of copper wire as a conducting path and a light bulb as a load. To make a more complicated circuits, like the one in your home, you must use a switch. A switch allows you to control the flow of current in an electrical circuit. These allow you to control the power in your home. Think of a light switch.

Types of Circuits

There are two main types electrical circuits, Parallel and SeriesTake a look at some of the differences between the two circuits.

Series Circuit Parallel Circuit
The circuit only has one path. All of the loads are connected side by side  on one path. There are several paths for electricity to flow through.Each load usually has it's own branch.
If there is a break in the path of electricity the entire circuit will not work. A break in one branch will not affect the other branches or appliances.
The resistance increases as each load is added. (R1+R1+R1= R3)

The resistance decreases as the loads increase.

The voltage ( potential energy that each electron has when it leaves the cell) stays the same. The voltage ( potential energy that each electron has when it leaves the cell) stays the same.
The current will be the same in all parts of the circuit.  It decreases as more loads are added. The more paths a circuit has the more current it demands from the power source. So if one light bulb is hooked up to each of 2 paths, they will both shine brightly.

Can you think of any examples of a Series or a Parallel circuit? Many circuits are a combination of both types of circuits.

Challenge: Try To Build These Circuits.

1.Draw a series circuit with one light bulb and one cell.

2.Draw a combined parallel and series circuit with 3 light bulbs and one cell. If light bulb A is off, B and C will not work. If A is on and B is on the circuit will work. If A and C are on, the circuit will work.

3. Draw a series circuit with two light bulbs, two cells and two switches. If switch A is on and B isn't, the circuit will work. If both are off, the circuit won't work.