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Chapter 17: Electricity

Chapter 17: Electricity. Section 1. Electric Charge and Force. Electric charge. An imbalance of protons and electrons Negative charge: more electrons than protons. Positive charge: more protons than electrons. SI unit : coulomb (C ). Opposite charges attract Like charges repel.

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Chapter 17: Electricity

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  1. Chapter 17: Electricity

  2. Section 1 Electric Charge and Force

  3. Electric charge • An imbalance of protons andelectrons • Negative charge: more electrons than protons. • Positive charge: more protons than electrons. • SI unit : coulomb(C)

  4. Opposite charges attract • Like charges repel

  5. Electric Force • attraction or repulsion between objects due to an electric field • The greater the electric charge, the greater the electric force. • As distance between objects increases, electric force decreases.

  6. Fields • Electric field: the space around a charged object in which another charged object experiences an electric force • One way to show an electric field is by drawing electric fieldlines.

  7. Field lines show direction and strength of each charge.

  8. Section 2 Current

  9. Electrical Potential Energy (V) • Movement of electric charge (often referred to as voltage) • SI unit: volts(V)

  10. Current (I) • how fast charges move (thru a wire) • SI unit: amperes(A) 1 ampere = 1 Coulomb in 1 second A = C/s

  11. Resistance (R) • caused by internal friction, which slows the movement of charges through a conducting material. • Brightness of light bulb depends on resistance of the filament. The filament of a 40 W light bulb has a higher resistance than the filament of a 100 W light bulb.

  12. Conductors have low resistance • Resistor: special type of conductor used to control current • Insulators have high resistance • Semiconductors have moderate resistance, depending on the materials they are made out of

  13. Calculating Resistance • This equation also known as Ohm’s law. • SI unit: ohms (Ω)

  14. Superconductors • Materials with zero resistance • Once a current is established in a superconductor, the current continues even if the applied voltage is removed. • One useful application of these materials is in superconducting magnets. These magnets are strong enough to levitate commuter trains above the tracks to eliminate friction.

  15. Section 3 Circuits

  16. Electrical Circuits • paths that allow the movement of charges

  17. Closed circuit: a complete path for electrons to flow along • Example: string of christmas lights plugged into the wall • Open circuit: an incomplete path • Example: string of Christmas lights that is not plugged in

  18. Switches are used to open and close a circuit

  19. Schematic Diagram • Drawing of a circuit that uses lines and symbols to represent wires and components

  20. Series circuits: single path for current • Parallel circuits: multiple paths for current

  21. Electrical Power • how fast electrical energy is converted into other forms of energy (often referred to as wattage) power = current × voltage P = IV • Power companies track energy consumption using the electric meters on the side of your house. • Cost of energy ranges from 5 to 20 cents per kilowatt-hour (the amount of energy delivered to your home in 1 hour at a rate of 1 kW).

  22. Fuse: device that contains a metal strip that melts when current in the circuit becomes too great

  23. Circuit breaker: a switch that opens a circuit automatically when the current exceeds a certain value

  24. Ground fault circuit interrupter (GFCI): special kind of electrical outlet that acts as a small circuit breaker. • often found in bathrooms and kitchens, where water is used near electricity

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