Electrical Functions 1.Power Supply Generates an electrical current in a circuit. Power Supply AdvantagesDisadvantagesExamples of Applications Battery Portable-Must be replaced -Contaminate the environment Watches, remote controls, mp3 players Electrical Outlet -Stable and long- lasting power supply -No GHG emissions (Hydro) -Appliance cannot be moved far from wall outlet -Stop working during power shortages -Flooding (hydro dams) TV, refrigerator, computer Photovoltaic Cell -Brings power to isolated areas -Portable -No GHG emissions Long life span -Depends on sunny conditions -Expensive Solar homes, calculators, solar cars

Try This! 1.There are two types of electric drills. One has a battery while the other has to be plugged into an electrical outlet. Explain how a battery and an electrical outlet can be classified as power supplies in a circuit. Paul’s calculator screen is dull when he sits in his living room where there is little light. When he walks into a well-lit room, the screen becomes brighter. What is the source of current in his calculator?

2. Conductors Allow electricity to run through them Ex: Wires, human body 3. Insulators Prevent electricity from passing through them They are poor conductors Ex: plastic, ceramic

Try This! 1. The procedure for a lab on electricity states that the wires connecting the switch must touch the metal part and not the plastic part of the switch. Why is it important to connect the wire to the switch correctly? 2. You are asked to build a circuit that will light up one light bulb with a switch. You have no wires available. The only materials in the classroom are listed below. Chalk Plastic fork Cardboard Nail Wooden spoon Ceramic coaster Metal knife Paperclip Which of the above materials could be used to complete the circuit? Explain your answer.

4. Protection To prevent short circuits or an overload, fuses and circuit breakers are connected to electrical circuits. They function by cutting current flow in the event of a power surge. Fuses Connected within the circuit Normally, the electric current passes through the fuse through a conductive filament. If the current becomes too intense, the conductive filament melts and breaks, preventing the current from flowing through the fuse. Must be replaced if fuse has blown Breakers Normally, the electric current passes through a metallic strip When the current becomes too intense, the metallic strip becomes hot and bends. The connection becomes broken. A switch is pulled to restore circuit operation.

Types of Circuits Some electric circuits contain a switch (control) which can “open” and “close” a circuit. 1.Closed Circuits -When an electric current can readily flow in a loop. 2. Open Circuits -When an electric current cannot readily flow in a loop. A CONTROL is a component which can open and close a circuit.

Which of the following circuit components is a control?