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Chapter 6 Electricity and Electric Circuits 6.1 What is a Circuit? Electricity means the flow of an electric current in wires or electric devices. Current carries energy over great distances but can be dangerous. Slide 2 Electrical circuit provides a path for electricity. Circuits exist in the natural world, like lightning. Electric current only flows in closed circuits. Slide 3 Switches are devices that turn circuits on/off. On = closed circuit. Off = open circuit. Slide 4 Circuits are made up of wires and different electrical parts. Circuit diagram -- drawing of electrical circuit. Electrical symbols are used to represent items in a circuit. Must Draw Wire Cell or battery Slide 5 A resistor is an electrical component that uses energy. In some cases, a resistor symbol is used in the circuit diagram instead of a light bulb. Slide 6 6.2 Charge Understanding and use of electricity is relatively recent. Faraday discovered the principles of the electric motor in 1830. Edison perfected the electric light in 1879. First experiments in electricity: People studied events like lightning and static electricity Slide 7 Electric charge is also a fundamental property of matter. Charge comes in two different kinds, positive and negative. Slide 8 Most objects are electrically neutral (same amount of positive and negative charges). If an object carries excess positive or negative charge it is electrically charged. Like charges repel Unlike charges attract Must Draw Slide 9 The unit of charge is the coulomb, named after the physicist that made the first accurate measurements of the forces between charges in 1783. Slide 10 Must Draw Electrical charges in atoms: + charge Proton - charge Electron Electroscopes detect charged objects.