Electric circuits

Components

A simple circuit comprises the power source, conductors, switch, and a resistor.

Some of the more common components are:

The cell/battery is the power source. A battery is made up of 2 or more cells. The battery pushes the current around the circuit. The higher the power, the quicker the rate at which a battery can do work.

Switch: It is a small gap in the circuit. There are several types of switches. A switch can be used to open or close a circuit i.e. it is used to turn a circuit on (closed) and off (open).

Lamp: An electrical current heat the filament in a bulb so that it gives out light.

Resistor: A resistor restricts or limits the flow of electrical current. A resistor has a resistance that does not change.

Variable resistor: Adjusting this resistor changes its resistance. A variable resistor is used in some dimmer switches and volume controls.

A motor spins round and a buzzer makes a buzzing sound. 

Connecting wires are usually made from copper because copper is an excellent conductor of electricity. 

An ammeter measures the current

A voltmeter measures the potential difference in a circuit. 

Electric circuits

An electric current will not flow if we do not have a power source (a cell, battery or power pack). It also won't flow if the circuit is not complete. One end of the power source must be joined to the other end by the wires and components of the circuit.

The simplest complete circuit is a piece of wire from one end of a battery to the other. An electric current can flow in the wire from one end of the battery to the other, but nothing useful happens. The wire just gets hot, and the battery goes flat.

To do something useful with the electric current, we need to put an electrical component into the circuit, such as a lamp or motor that can use the current to make something happen.

A switch is usually added to the circuit, so that the circuit can be broken, and the electric current will stopped when necessary.  

Circuit diagrams

The idea of a circuit diagram is to use circuit symbols instead of drawing each component in the circuit. Always try to make the wires straight lines, and don't be tempted to make them wiggly.

The whole point is to make it easier to see what is connected to what. Here you can see how the symbols for a cell (not a battery!) and a lamp look in a circuit diagram.

When you are drawing circuits, you MUST:

1.     Use a sharp pencil and a ruler

2.     Make sure your lines are straight and all angles are at 90°

3.     Leave no gaps between wires and /or components