Lesson 2 Electrical Circuits

Electricity on the Move part 2 Electricity is due to the movement of electrons. When this flow of electrons becomes a steady flow it is known as electric current.

Closed Circuit In order for electricity to flow it must be in a closed circuit. Electric current can only flow in a closed circuit. Closed circuit – a complete path for the flow of electric current.

Open Circuit A circuit with a gap ore break is called an open circuit. Electric current cannot glow in an open circuit.

How can you tell if a circuit is open or closed?

Every working electric circuit has the same three basic parts. 1. A Source of electric energy: In the diagrams above the battery is the source. 2. A Load: A load changes electrical energy into another kind of useful energy. In the circuits above the light bulb is the load. 3. A Conductor: A conductor is a pathway for electricity to flow through a circuit. In the circuits above, the wire is the conductor.

A circuit that has these three basic parts connected together is called a complete circuit. Electric current will always flow in a complete, closed circuit. But sometimes you do not want current to flow. It is useful to have an easy way to control the circuit. For this reason, most circuits contain a forth part. 4. A Switch: A switch is a device that lets you open and close a circuit. A switch lets you control when a current flows though a circuit.

Electric Circuit Diagrams and Symbols

There are set rules when drawing circuit diagrams, doing this makes them universal for anyone looking at them and it makes them easier to read and follow. 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. All lines are drawn straight with right angled corners for turns. All other parts of the circuit follow the symbols shown below.

Electric Circuit Diagrams and Symbols Conductor or wire ___________________ To pass current very easily from one part of a circuit to another. Cell-Supplies electrical energy The positive end is bigger than the negative end. Battery –supplies electrical energy Contains more than one cell

Electric Circuit Diagrams and Symbols DC Source- Electrical energy source DC = Direct current, always flows one way AC Source - Electrical energy source AC = Alternating current, continually changing direction Ground – A connection to earth

Electric Circuit Diagrams and Symbols Switch - An on-off switch allows current to flow only when it is in the closed (on) position Lamp- A transducer which converts electrical energy to light Resistor- A resistor restricts the flow of current,

Practice lab Materials Arrange all of the items until you can get the bulb to light up. Draw a picture of the set up using proper schematic circuit diagram symbols. Label each item in the diagram 1.5 v DC battery2 wires with alligator clips Light bulb

Compare your drawing to other students. How are all the successful drawings similar? What arrangements did not make the bulb light up? Why didn’t they work?

Electric Circuit Lab