Electricity

Electric Charges and Static Electricity Two types of charges are positive and negative. ( + - ) Static electricity is the build up of charges on an object. These charges do not flow continuously. Positive charged particles are called protons, negative charged particles are called electrons and neutral particles are called neutrons. These particles make up the atom (smallest particle of matter) If an object gains electrons, its charge becomes negative. If an object loses electrons, its charge becomes positive.

Electric Current Electric current is the continuous flow of electric charges (electrons) through a material. Current is measured in amps, amperes, or A using an ammeter.

Electric Circuit To produce electric current, charges must flow continuously from one place to another An electric circuit is a complete, unbroken path through which electric charges can flow.

Features of a Circuit All electric circuits have the same basic features. First, circuits have devices that are run by electrical energy. Ex: Light Bulb, Radio, Computer These devices are also called resistors, because they resist (slow down) the flow of electric current and may be shown as a resistor in a circuit diagram:

Features of a Circuit Second, a circuit has to have a voltage source. Voltage is the difference in electrical potential energy between two places in a circuit. Voltage pushes the electrons. It’s measured in volts (V) using a voltmeter. Two examples are:

Features of a Circuit Third, electric circuits are connected by conducting wires. They allow charges to flow from the voltage source to the device that runs on electric current and back to the energy source

Features of a Circuit A switch is often included in a circuit to control the current in the circuit. Using a switch, you can turn a device on or off by closing or opening the circuit.

Circuit Diagram

Conductors and Insulators Conductors are materials through which charges can flow easily. The atoms in conductors contain electrons that are loosely bound. Examples: Copper and Aluminum Insulators are materials through which charges cannot flow easily. Their electrons are bound tight to their atoms. Examples: Rubber and Plastic

Resistance Resistance is the measure of how difficult it is for charges to flow. Resistance is measured in ohms, or omega. There are four factors that determine the resistance in any wire. They are: Materials (conductors have less resistance than insulators) Length (short wires have less resistance than long wires) Diameter (thick wires have less resistance than thin wires) Temperature (cold wires have less resistance than hot wires)

Series Circuits Only one path for current to take If one bulb is removed or goes out, all bulbs go out Lights become dimmer as more bulbs are added (more resistance)

Parallel Circuits There are multiple pathways for current to take If one bulb is removed or goes out, the other bulbs remain lit Lights remain the same brightness as more bulbs are added (less resistance)

Electrical Safety Circuit Breaker – a safety switch that breaks the circuit when the current gets too high Fuse – a safety device that contains a thin strip of metal that melts when current gets too high Lightning Rod – a safety device made of a metal rod mounted on the roof of a building to protect the building