1. Electrical Energy Generation and Transmission Physical Science Chapter 21 Section 3

2. Science Journal Entry 46 Explain the difference between Earth’s geographic north pole and Earth’s magnetic north pole. Be sure to mention magnetic declination. Explain the difference between Earth’s geographic north pole and Earth’s magnetic north pole. Be sure to mention magnetic declination.

3. Science Journal Entry #47 Explain how the strength of an electromagnet may be increased. Explain how the strength of an electromagnet may be increased.

4. Science Journal Entry 48 Describe the path that electricity takes from the power plant to your home. Describe the path that electricity takes from the power plant to your home.

5. Science Journal Entry #49 Explain the difference between a step-up and a step- down transformer. Explain the difference between a step-up and a step- down transformer.

6. Generating Electric Current Electromagnetic Induction is the process of generating a current by moving an electrical conductor relative to a magnetic field. Electromagnetic Induction is the process of generating a current by moving an electrical conductor relative to a magnetic field. The English scientist Michael Faraday (1791-1867) discovered electromagnetic induction in 1831. The English scientist Michael Faraday (1791-1867) discovered electromagnetic induction in 1831. According to Faraday’s law, if a coil is a part of a complete circuit, changing the magnetic field through the coil of wire will induce a voltage in the coil producing a current. According to Faraday’s law, if a coil is a part of a complete circuit, changing the magnetic field through the coil of wire will induce a voltage in the coil producing a current. If you place a magnet in a coil, no current is produced if it does not move but if either the coil or the magnet is moving an alternating current will be produced. If you place a magnet in a coil, no current is produced if it does not move but if either the coil or the magnet is moving an alternating current will be produced.

7. Question Set One 1. What is the process of generating a current by moving an electrical conductor relative to a magnetic field? 1. What is the process of generating a current by moving an electrical conductor relative to a magnetic field? 2. Who discovered electromagnetic induction in 1831? 2. Who discovered electromagnetic induction in 1831? 3. If a coil is a part of a complete circuit, changing the magnetic field through the coil will induce a _____ in the coil producing a ____. 3. If a coil is a part of a complete circuit, changing the magnetic field through the coil will induce a _____ in the coil producing a ____. 4. T or F If you place a magnet in a coil, no current is produced if it moves. 4. T or F If you place a magnet in a coil, no current is produced if it moves. 5. What is required to produce an alternating current by electromagnetic induction? 5. What is required to produce an alternating current by electromagnetic induction?

8. Generators The electric energy used in homes and businesses is produced in large power plants by generators. A generator is a device that converts mechanical energy into electrical energy by rotating a coil of wire in a magnetic field. The two types of generators are AC and DC generators. Most power plants today use AC generators. A wire coil in the generator is attached to metal bands called slip rings. The rings are in contact with metal brushes that are in turn attached to a circuit. As the loop of wire is rotated the magnetic field induces a current in the wire. It is called AC for alternating current since the electric current alternates its direction. The electric energy used in homes and businesses is produced in large power plants by generators. A generator is a device that converts mechanical energy into electrical energy by rotating a coil of wire in a magnetic field. The two types of generators are AC and DC generators. Most power plants today use AC generators. A wire coil in the generator is attached to metal bands called slip rings. The rings are in contact with metal brushes that are in turn attached to a circuit. As the loop of wire is rotated the magnetic field induces a current in the wire. It is called AC for alternating current since the electric current alternates its direction.

9. DC Generators In a DC (direct current) generator, the commutator replaces the slip rings. Although an alternating current is induced in the wire, direct current is produced. One side of the commutator contacts a brush and when the current is induced in the other direction the other side of the commutator touches the other brush. This moves it in a circular direction producing direct rather than alternating current. In a DC (direct current) generator, the commutator replaces the slip rings. Although an alternating current is induced in the wire, direct current is produced. One side of the commutator contacts a brush and when the current is induced in the other direction the other side of the commutator touches the other brush. This moves it in a circular direction producing direct rather than alternating current.

10. Question Set Two 6. What is a device that converts mechanical energy into electrical energy by rotating a coil of wire in a magnetic field? 6. What is a device that converts mechanical energy into electrical energy by rotating a coil of wire in a magnetic field? 7. What are the two types of generators? 7. What are the two types of generators? 8. Which is used by most power plants today? 8. Which is used by most power plants today? 9. What are the metal bands that the wire coil in a generator is attached to called? 9. What are the metal bands that the wire coil in a generator is attached to called? 10. The rings are in contact with ___ ____that are in turn attached to a ______. 10. The rings are in contact with ___ ____that are in turn attached to a ______. 11. Why are AC generators called AC? 11. Why are AC generators called AC? 12. What takes the place of the slip rings in a DC generator and what type of current is produced? 12. What takes the place of the slip rings in a DC generator and what type of current is produced? 13. T or F The commutator comes in contact with the metal brushes on both sides of it but not simultaneously. 13. T or F The commutator comes in contact with the metal brushes on both sides of it but not simultaneously.

11. Transformers Since electricity is transmitted through power lines at very high voltages, the voltage has to be transformed into 240-volt current that enters your home. A transformer is a device that increases or decreases the voltage and current of two linked AC circuits. AC (alternating current) induces a constantly changing magnetic field. The changing magnetic field induces an alternating current in a nearby coil with a different number of turns. Since electricity is transmitted through power lines at very high voltages, the voltage has to be transformed into 240-volt current that enters your home. A transformer is a device that increases or decreases the voltage and current of two linked AC circuits. AC (alternating current) induces a constantly changing magnetic field. The changing magnetic field induces an alternating current in a nearby coil with a different number of turns. DC current can not transmit power far enough without overheating the wires. Only AC current is able to transmit a lower current at a higher voltage. DC current can not transmit power far enough without overheating the wires. Only AC current is able to transmit a lower current at a higher voltage.

12. Types of Transformers There are two types of transformers: the step- down transformer and the step up transformer. A step-down transformer decreases voltage and increases current. A step-up transformer increases voltage and decreases current. There are two types of transformers: the step- down transformer and the step up transformer. A step-down transformer decreases voltage and increases current. A step-up transformer increases voltage and decreases current. Each transformer has two sets of coils wrapped around a ring-shaped iron core. In the primary coil, the current creates a changing magnetic field in the iron core. Since this iron core is also inside the secondary coil, the changing field induces an alternating current in the secondary coil. Each transformer has two sets of coils wrapped around a ring-shaped iron core. In the primary coil, the current creates a changing magnetic field in the iron core. Since this iron core is also inside the secondary coil, the changing field induces an alternating current in the secondary coil.

13. Question Set Three 14. What is a device that increases or decreases the voltage and current of two linked AC circuits? 14. What is a device that increases or decreases the voltage and current of two linked AC circuits? 15. T or F AC (alternating current) induces a constantly changing magnetic field. 15. T or F AC (alternating current) induces a constantly changing magnetic field. 16. Why is AC current better than DC current at transmitting power at greater distances? 16. Why is AC current better than DC current at transmitting power at greater distances? 17. AC current is able to transmit a _____ current at a higher _______. 17. AC current is able to transmit a _____ current at a higher _______. 18. What are the two types of transformers and how are they different? 18. What are the two types of transformers and how are they different? 19. In what coil does the current generate a magnetic field and in which coil is the alternating current induced? 19. In what coil does the current generate a magnetic field and in which coil is the alternating current induced?

14. Changing Voltage and Current The number of turns in the primary and secondary coils determines the voltage and current. The number of turns in the primary and secondary coils determines the voltage and current. To calculate the voltage, divide the number of turns in the secondary coil by the number of turns in the primary coil. This gives you the ratio of the output voltage to the input voltage. To calculate the voltage, divide the number of turns in the secondary coil by the number of turns in the primary coil. This gives you the ratio of the output voltage to the input voltage. Electric power (in watts) is equal to the current (amps) x the voltage. Electric power (in watts) is equal to the current (amps) x the voltage. P(watts) = I (amps) x V(volts) P(watts) = I (amps) x V(volts) Since the power must be the same in the primary coil and secondary coil, if voltage increases in the secondary coil, the current must decrease in the same ratio. Since the power must be the same in the primary coil and secondary coil, if voltage increases in the secondary coil, the current must decrease in the same ratio.

15. Question Set Four 20. What determines the voltage and current in the transfer? 20. What determines the voltage and current in the transfer? 21. How is the voltage calculated and what ratio does that give? 21. How is the voltage calculated and what ratio does that give? 22. What does the formula P=IxV stand for and what units are used? 22. What does the formula P=IxV stand for and what units are used? 23. T or F Power has to be the same in the primary coil as in the secondary coil. 23. T or F Power has to be the same in the primary coil as in the secondary coil. 24. If voltage increases, the current has to ______. 24. If voltage increases, the current has to ______. 25. If current increases, the voltage has to ______. 25. If current increases, the voltage has to ______.

16. Electrical Energy Sources and Turbines Most of the electrical energy generated in the United States is produced by coal as an energy source. Other sources for electrical energy are water (hydroelectric), nuclear energy, wind, natural gas and petroleum. A turbine can convert energy from these sources into electrical energy. A turbine is a device with fanlike blades that turn when pushed by water or steam. Water is heated to provide the steam needed to turn turbines. It may be heated by the burning of fossil fuels or nuclear reactions. Water pouring over a dam can also turn a turbine.

17. From the Power Plant to Your Home The turbine may turn the coils of a generator or it may spin magnets around the coils of wire to produce electrical energy. The energy from the power plant is stepped up to hundreds of thousands of volts. After the voltage travels along the high voltage lines, it is stepped down by transformers at a substation to a few thousand volts. The electrical energy is distributed to neighborhoods after it is stepped down to between 220 and 240 volts. Though most appliances use 120 volts, an electric stove uses 240 volt circuits. The energy from the power plant is stepped up to hundreds of thousands of volts. After the voltage travels along the high voltage lines, it is stepped down by transformers at a substation to a few thousand volts. The electrical energy is distributed to neighborhoods after it is stepped down to between 220 and 240 volts. Though most appliances use 120 volts, an electric stove uses 240 volt circuits.

18. Question Set Five 26. What is most of the electrical energy in the US produced by? 26. What is most of the electrical energy in the US produced by? 27. What are five other sources for electrical energy? 27. What are five other sources for electrical energy? 28. What 28. What is a device with fanlike blades that turn when pushed by water or steam? 29. In what two ways does a turbine produce electrical energy? 29. In what two ways does a turbine produce electrical energy? 30. The energy from the power plant is ____ ___ to hundreds of thousands of volts. 30. The energy from the power plant is ____ ___ to hundreds of thousands of volts. 31. How many times will the voltage be stepped down and to what voltage? 31. How many times will the voltage be stepped down and to what voltage? 32. What is the difference between the amount of voltage that most appliances have to the electric stove? 32. What is the difference between the amount of voltage that most appliances have to the electric stove?