To operate electrical devices, you need a steady flow of electrons. Unlike static electricity, a...

Current Electricity and Electric Circuits

To operate electrical devices, you need a steady flow of electrons. Unlike static electricity, a flow of electrons moves continuously as long as two conditions are met.

1. The flow of electrons requires an energy source.

Current Electricity

2. The electrons will not flow unless they have a complete path to flow through. ◦ This path is called an electrical circuit.

The continuous flow of electrons in a circuit is called current electricity.

Electrons flow from the negative terminal to the positive terminal

Think of electron in a wire like water in a hose. ◦ If the hose already has water in it, once you

turn the tap on water comes out the other end.

How Electrons Transfer Energy in a Circuit

◦ Electrons in a wire work in a similar way. ◦ When an energy source is connected to a

circuit, electrons in the conductor “push” or repel other electrons nearby.

◦ As soon as one electron starts to move at one end of the wire, it pushes the next one, which pushes the next one and so on.

◦ By pushing the first electron, you make the last electron move

There are two ways that we can produce current electricity.

Direct Current (DC) Electrons flow from the negative

terminal to the positive terminal. ◦ Example- Battery.

◦ Draw this diagram in the blank Square provided

Forms of Current Electricity (P 515)

Alternating Current (AC) Electrons move back and forth,

alternating their direction many times every second.

AC is used in more applications than DC as it is more efficient when traveling long distances.

AC is used in all homes and work places.

Forms of Current Electricity (P 515)

A circuit includes:

1. Energy source – battery or generator 2. Conductor – allows the current to move

through the circuit

Electric Circuits (P 509, 551)

Load - a device that converts electrical energy to another form of energy.

Example: Light bulb, motor, heater, etc. The figure below shows a light bulb as the load. It converts electrical energy to light and heat

Switch (optional) - a device that turns the circuit on or off by closing or opening the circuit.

When the switch is closed, the circuit is complete and electrons can flow.

An open switch means there is a break in the path, so the electrons cannot flow through the circuit.

There are set rules when drawing circuit diagrams, doing this makes them universal for anyone looking at them.

It also allows only a few basic symbols to represent many different types of switches, loads and energy sources.

The drawings that follow these rules are called Schematic Circuit Diagrams.

Electric Circuit Diagrams and Symbols

All lines are drawn straight with right angled corners for turns.

All other parts of the circuit follow the symbols shown on the following slides.

Electric Circuit Diagrams and Symbols