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Transcript
Electrical Energy State Correlation: 2d Discuss Imagine a world without electricity What is Electricity? • Electricity is a form of energy produced by the flow of electrons from one point to another. • Conductors are materials through which electricity moves easily – Most metals are good conductors • Ex. Copper & Aluminum • Most wires in homes are made from copper • Insulators are substances that are poor conductors and do not allow electrons to flow through them – Ex. Rubber, glass, plastic, air, & wood Law of Electric Charges Two types of charges: Positive & Negative • Like charges repel + + - • Unlike Charges attract +- Electric Currents • Current electricity is a continuous flow of electricity or the amount of charge that moves past a certain point each second – SI unit for current is the ampere or amp Controlling a Current • Voltage: in a battery it is the measure of how much electrical potential energy each electron can gain – Standard Unit: Volts • Resistance: the measure of how difficult it is for electrons to flow through a material – Standard unit: Ohms – Insulators have a higher resistance than conductors Affecting Resistance • Length of a conductor – The longer the wire the greater the resistance – Analogy: Long hose verses a short hose – which one will water flow from the fastest? • Size/width of a conductor – The thinner the wire the greater the resistance – Analogy: thick hose verses a thin hose – which one will water flow from the fastest? • Real worlds example: – long, thin coiled tungsten wires are used in light bulbs because it has a high melting point – Electric Companies have to use high voltage to send electricity in the long wires from the power plant to your house, but the a lower voltage is required for electricity to flow throughout your house Volts Which circuit will be brighter? Explain Review • Which of the following has the greatest resistance? Least Resistance? – Short, thick wire – Long, thick wire – Short, thin wire – Long, thin wire (least resistance) (greatest resistance) Currents Flow In Circuits • An electric circuit is a complete path for the flow of electricity – Open circuits have a break in the path – Closed circuits have no breaks in the path Parts of a Circuit • Energy Source: the object that pushes electric charges through a closed circuit – Batteries have a positive and a negative terminal. One terminal repels charges while the other terminal attracts charges providing the push that keeps the electric charges moving – The greater the voltage the greater the push • Load/device: the object that the electrical energy is delivered to (light bulb) Parts of a Circuit • Wires: connect the energy source to the load – Often made of copper and insulated with plastics or rubber • Switch: made to open and close a circuit by bringing together or separating two pieces of metal Circuit Symbols Types of Circuits • Series Circuit: single path of electricity through devices attached to the circuit – If one device stops working the circuit path of electricity is broken so no other devices work Types of Circuits • Parallel Circuit: has two or more devices/loads wired so that the electricity flows through separate branching paths to each device – If one device stops working the other devices continue to work through their own path of electricity Comparing & Contrasting Circuits Protecting Electric Circuits • In a circuit, the more devices, the more current & the more amps the more heat energy is produced • Fuses/circuit breaker: a device that protects a circuit from overheating and causing a fire – If the current becomes too large a piece of metal melts or a switch opens the circuit to stop the current Energy Transformations • Law of Conservation of Energy: states that energy cannot be created nor destroyed, but it can change from one form to another • Chemical transformations – Batteries in a flashlight – Chemical to electrical to light • Electrical transformation – Plug in a Blow-dryer – electrical to heat • Electrical transformation – Electric pencil sharpener – electrical to mechanical Generating Electricity: where does electricity come from? • Generators: device that spins coiled wire within a magnetic field producing electricity by transferring heat energy to mechanical energy – The mechanical energy of a spinning turbine is transformed into electrical energy for human use – Primary method for producing the electricity in homes, schools, & the community Energy Production • Most Electricity is produced in power plants by burning fossil fuels to boil water which produces steam that turns a turbine to generate electricity. How a Generator Works Power Grid • A power grid is a transmission network that connects power plants to multiple substations near a populated area. – Allows distant energy sources (such as hydroelectric power plants) to be connected to consumers in population centers Power Grid Transformer • Device that transfers electrical energy from one circuit to another & changes the voltage by increasing or decreasing it. – Helps monitor the operation of the power grid and measures current. Transformer Path of Electricity through a Power Grid • Power Plant • Substation ( there are several along the way) • Transmission Lines ( high & low voltage) • Transformer (lowers voltage before entering the home) • Junction Box on the home (brings it into the home) • Outlet (sends it to electrical devices) • Electric circuit for a blow dryer