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Electric Power and Electrical Energy

Section 3 Circuits. Chapter 16. Electric Power and Electrical Energy. Electrical energy is the energy that is associated with charged particles because of their positions. Electric power is the rate at which electrical energy is used in a circuit.

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Electric Power and Electrical Energy

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  1. Section 3 Circuits Chapter 16 Electric Power and Electrical Energy • Electrical energy is the energy that is associated with charged particles because of their positions. • Electric power is the rate at which electrical energy is used in a circuit. • The rate at which electrical work is done is calledelectric power. • The SI unit for power is the watt (W). • 1 W = 1 A  1 V

  2. Section 3 Circuits Chapter 16 Electric Power and Electrical Energy, continued • If you combine the electric power equation above with the equation V = IR, the power lost, or dissipated, by a resistor can be calculated. • Electric companies measure energy consumed in kilowatt-hours. • 1 kW•h = 3.6  106 J.

  3. Section 3 Circuits Chapter 16 Equation for Electric Power

  4. Section 3 Circuits Chapter 16 Math Skills • Electric Power When a hair dryer is plugged into a 120 V outlet, it has a 9.1 A current in it. What is the hair dryer’s power rating? 1. List the given and unknown values. Given: voltage, V = 120 V current, I = 9.1 A Unknown: electric power, P = ? W

  5. Section 3 Circuits Chapter 16 Math Skills, continued 2. Write the equation for electric power. power = current × voltage P = IV 3. Insert the known values into the equation, and solve. P = (9.1 A)(120 V) • P = 1.1 × 103 W

  6. Section 3 Circuits Chapter 16 Fuses and Circuit Breakers • When electrical wires carry more than a safe level of current, the circuit is said to beoverloaded. • Ashort circuitcan happen if a wire’s insulation wears down, two wires may touch, creating an alternative pathway for current. • Fuses melt to prevent circuit overloads. • A fuse an electrical device that contains a metal strip that melts when current in the circuit becomes too great.

  7. Section 3 Circuits Chapter 16 Fuses and Circuit Breakers • Circuit breakers open circuits with high current. • A circuit breaker a switch that opens a circuit automatically when the current exceeds a certain value. • The circuit breaker acts as a switch. • Unlike fuses, circuit breakers can be reset by turning the switch back on.

  8. Section 3 Circuits Chapter 16 Fuse

  9. Section 3 Circuits Chapter 16 Concept Mapping

  10. Standardized Test Prep Chapter 16 Understanding Concepts 1. A 12-volt battery is connected to a light bulb that has a resistance of 240 ohms. Calculate the amount of current in amperes drawn by the circuit. A. 0.05 A B. 0.5 A C. 2.0 A D. 20.0 A

  11. Standardized Test Prep Chapter 16 Understanding Concepts, continued 1. A 12-volt battery is connected to a light bulb that has a resistance of 240 ohms. Calculate the amount of current in amperes drawn by the circuit. A. 0.05 A B. 0.5 A C. 2.0 A D. 20.0 A

  12. Standardized Test Prep Chapter 16 Understanding Concepts, continued 2. Which of the following statements is true? F. Electrical forces exist between any two neutral particles. G. Electrical forces exist between any two charged particles. H. Electrical forces exist only between particles with the same charge. I. Electrical forces exist only between particles with opposite charges.

  13. Standardized Test Prep Chapter 16 Understanding Concepts, continued 2. Which of the following statements is true? F. Electrical forces exist between any two neutral particles. G. Electrical forces exist between any two charged particles. H. Electrical forces exist only between particles with the same charge. I. Electrical forces exist only between particles with opposite charges.

  14. Standardized Test Prep Chapter 16 Understanding Concepts, continued 3. What happens to an object that is charged by induction? A. It acquires excess electrons. B. It remains electrically neutral. C. It acquires a net charge from the object that is inducing the charge. D. A current exists between it and the object that is inducing the charge.

  15. Standardized Test Prep Chapter 16 Understanding Concepts, continued 3. What happens to an object that is charged by induction? A. It acquires excess electrons. B. It remains electrically neutral. C. It acquires a net charge from the object that is inducing the charge. D. A current exists between it and the object that is inducing the charge.

  16. Standardized Test Prep Chapter 16 Understanding Concepts, continued 4.A stream of water is deflected when a negatively charged rod is held close to it. Use the concept of induced charge to explain what happens.

  17. Standardized Test Prep Chapter 16 Understanding Concepts, continued 4.A stream of water is deflected when a negatively charged rod is held close to it. Use the concept of induced charge to explain what happens. Answer: A charge is induced on the water by the charged rod. Attraction between the charged part of the stream and the rod deflects the flow.

  18. Standardized Test Prep Chapter 16 Understanding Concepts, continued 5.How does a fuse protect a circuit from overloading?

  19. Standardized Test Prep Chapter 16 Understanding Concepts, continued 5.How does a fuse protect a circuit from overloading? Answer: The fuse has a thin wire with a low melting point. When electrical resistance increases the temperature too high, it melts and breaks the circuit.

  20. Standardized Test Prep Chapter 16 Reading Skills In 1909 Robert Millikan measured the charge on an electron in what is known as the oil-drop experiment. He sprayed oil droplets into a chamber. Two plates with opposite charges produced an electric field. Some of the drops acquired a negative charge. The field was adjusted so there was an upward force equal to the downward pull of gravity. From the strength of this force, Millikan could calculate the amount of the electric charge on the drop. 6. Analyze how the electric field could cause an oil drop to float inside the chamber.

  21. Standardized Test Prep Chapter 16 Reading Skills, continued 6. Analyze how the electric field could cause an oil drop to float inside the chamber. Answer: Electrical forces between the charged particle an the charged plates balance the downward pull of gravity.

  22. Standardized Test Prep Chapter 16 Interpreting Graphics 7. Which metal would be the best choice for a power line, based on electrical resistance? F. aluminum G. iron H. lead I. silver

  23. Standardized Test Prep Chapter 16 Interpreting Graphics 7. Which metal would be the best choice for a power line, based on electrical resistance? F. aluminum G. iron H. lead I. silver

  24. Standardized Test Prep Chapter 16 Interpreting Graphics 8. Which metal would most likely be then best substitute for the tungsten filament in an incandescent light bulb based on resistance? A. aluminum B. iron C. lead D. silver

  25. Standardized Test Prep Chapter 16 Interpreting Graphics 8. Which metal would most likely be then best substitute for the tungsten filament in an incandescent light bulb based on resistance? A. aluminum B. iron C. lead D. silver

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