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GRADE 7 Name: Definitions: Electricity is the flow of electrical energy or charge. These charges move from one place to another in an electric circuit, carrying electrical energy. A circuit is the actual pathway the electricity flows along, from a power source, to where it is needed and back to the power source. A simple circuit consists of these components: • An energy source (cell or battery) • A light bulb (or item which changes the electrical energy into another form of energy for a certain purpose) • Connectors (wires) • A switch All of these components must be connected for energy to flow through the circuit. If the switch is open (off ) the circuit is open and electricity will not flow through it. If the switch is closed (on), the circuit is closed and complete and all of the components are connected, so electricity can flow. CELLS CONNECTORS LIGHT BULBS SWITCHES Source of electrical energy. Have a number on them which tell us their voltage. Voltage tells us about the cells ability to “push” energy through the circuit. Have positive and negative poles. Connect all of the components together and allow energy to flow through the circuit. Conduct electricity. It is safest if these wires are insulated (coated) with plastic. This prevents shocking and short circuits. Indicate whether or not electricity is flowing through the circuit. Also have a voltage reading. Voltage in the circuit (from the cell) must not exceed the bulb’s voltage or it will burn out. Open or close the circuit. Many different types including push/press switches, and those that toggle as well as home-made switches. A switch is any point in the circuit which you use to connect or break the circuit. © e-classroom 2014 www.e-classroom.co.za Grade 7 Term 3 Technology: Electrical Systems and Control; Simple Electrical Circuit Simple Electrical Circuit GRADE 7 Each component is represented in circuit diagrams using a universal symbol. We use these symbols because the real-life objects may differ. For example, picture a light bulb in your mind and draw a picture of it. Now ask a friend to do the same. You will note that these two drawings will look quite different. Here are the symbols we use to represent the components of an electric circuit: Component Picture Symbol Cell Battery(2 or more cells connected) (Long line = positive Short line = negative) Connectors Switch (open) Switch (close) Light bulb ACTIVITY: Complewte in your class workbook 1) Build a simple electric circuit using the following components: 2 x AA cells (1,5V); a 2xAA cell holder; a light bulb; a switch and connectors. 2) Draw a circuit diagram to represent your simple circuit. 3) Explain what happens when the switch is closed. 4) Explain what happens when the switch is open. © e-classroom 2014 www.e-classroom.co.za Grade 7 Term 3 Technology: Electrical Systems and Control; Simple Electrical Circuit Circuit diagrams GRADE 7 Activity: 1) Build a simple electric circuit using the following components: 2 x AA cells (1,5V); a 2xAA cell holder; a light bulb; a switch and connectors 2) Draw a circuit diagram to represent your simple circuit. Drawing must include two cells, a light bulb and a switch (which can be drawn open or closed). The arrow is important as it shows the flow of current, which is always from the positive pole, through the circuit and back to the negative pole. 3) Explain what happens when the switch is closed. When the switch is closed, the circuit is complete or connected. Energy can flow from the cells through the circuit. The light bulb lights up because there is a flow of electricity. 4) Explain what happens when the switch is open. When the switch is open, the circuit is incomplete or disconnected. Energy cannot flow from the cells through the circuit. The light bulb does not light up because there is no flow of electricity. © e-classroom 2014 www.e-classroom.co.za Grade 7 Term 3 Technology: Electrical Systems and Control; Simple Electrical Circuit Answer sheet