Understanding Electricity and Magnetism: Principles and Applications

1. STANDARD S8P5. Students will recognize characteristics of gravity, electricity, and magnetism as major kinds of forces acting in nature. b. Demonstratethe advantages and disadvantages of series and parallel circuits and how they transfer energy. c. Investigateand explainthat electric currents and magnets can exert force on each other.

2. Review Direct Current- charges always flow in the same direction Alternating Current- charges continually shift from flowing in one direction to flowing in the reverse direction

4. Tech Terms 1.Circuit 2.Electrical Current 3.Voltage 4.Resistance

5. ELECTRIC CURRENT (I) • Rate at which electrical charges (electrons) pass a given point • measured in amperes or amps (A)

6. VOLTAGE (V) or Electrical Potential A measure of how much work is needed to move a charge (current) between two points. • Potential difference between two points in a circuit • measured in volts (v)

7. RESISTANCE (R) • opposition to the amount of current in a wire OR “electric friction” • measured in ohms(Ω)

8. Generating DC Electricity • Cell or Battery - device produces electric current by converting chemical or radiant energy into electrical energy • Thermocouple- device produces electric current by converting thermal energy into electrical energy • Photocells- device produces electric current by converting light energy into electrical energy

9. Generating AC Electricity • AC current is produced by a generator, usually at a power plant. • Power plants convert moving water, fossil fuels, nuclear power, wind, solar energy into electrical energy

10. Essential Question • Why are some substances magnetic and other substances are not?

11. The Key Idea • A magnet is an object that is surrounded by a magnetic field and that has the property of attracting iron.

12. The spinning electrons in every atom produce tiny magnetic fields. In most materials the fields of atoms point in random directions so the magnetic fields cancel each other out.

13. In some materials the magnetic fields of electrons align with one another. A cluster of atoms with magnetic fields lined up in the same way is known as a magnetic domain.

14. How is a magnet made? • For an object to be magnetic, most of its domains (tiny magnetic fields produced by spinning electrons) must be aligned in the same direction.

16. A pole is the area of a magnetic where the magnetic effect is the strongest. • Every magnetic has two poles – often called the north and south pole.

18. Magnets can produce: • An attractive force (pulling) when unlike magnetic poles attract • A repulsive force (pushing) when like magnetic poles repel. Sounds a lot like the Law of Charges!

19. Magnetic force is caused by a magnet attracting (pulling) other magnets and some other materials (e.g. iron and steel)

20. Magnetic force is also caused by a magnet repelling (pushing) other magnets and some other materials (e.g. iron and steel)

21. A magnetic field is area around the magnet in which magnetic forces act; concentrated into a pattern of lines that extend from the magnet’s north pole to its south pole.

22. Magnetic energy results when an object is moved a distance by a magnetic force. • Two Kinds of magnets: • a) Temporary - easy to magnetize and demagnetize easily • b) Permanent - hard to magnetize or demagnetize

23. Essential Question What is the difference between a motor and a generator?

24. Essential Question What is the difference between a motor and a generator?

25. Key Concept • A compass points to the Earth’s North Pole because the Earth acts like a giant magnet. (The core of the Earth is mostly molten iron.)

26. Key Concept • Earth has a north magnetic pole and a south magnetic pole.

27. Key Concept • Earth’s magnetic poles are not exactly the same locations as the geographic poles (axis where the Earth spins).

29. A compass can be used to find directions because its needle lines up with the Earth’s magnetic poles.

31. What would happen to the magnetic properties of a bar magnetic if you cut it into two pieces?

32. How can a magnet lose its magnetic properties? • Losing Magnetic Alignment by: • a) Dropping a magnet or hitting it too hard • b) Putting magnet in opposite field for too long • c) Increasing the temperature

33. Key Concept • An electromagnet is a coil of current-carrying wire that acts as a magnet that can be turned on and off.

34. Solenoid = a current-carrying coil of wire with many loops. • When a solenoid is turned on, a magnetic field is created.

35. If a piece of iron or other ferromagnetic material is wrapped by the coils of wire in a solenoid, a magnet is created when the current is turned on.

36. The strength of an electromagnet can be increased by: • 1)Increasing the electric current in the solenoid • 2)Increasing the number of coil loops around the ferromagnetic material • 3)Using a stronger ferromagnetic material (more iron content)

37. Examples of Electromagnet Uses: • a)A doorbell or an alarm • b)Moving junk cars • c)Recording data on your computer • d)Reading the magnetic strip on the back of a credit card

38. a) A doorbell or an alarm

39. b) Moving junk cars

40. d) Reading the magnetic strip on the back of a credit card

41. Big Idea about Electricity and Magnetism Electromagnetism - interaction between electricity and magnetism - Magnetic forces arise from the movement of electrical charge. - Electrical forces arise from the movement of a magnet (induced current)

42. Motors An electric motor is a device that changes electrical energy into mechanical energy. All electric motors have an armature—a loop or coil of wire that can rotate. The armature is mounted between the poles of a permanent magnet or electromagnet.

44. Generators • A generator is a device that uses electromagnetic induction to change mechanical energy into electrical energy. • An electric current is made when a magnet moves in a coil of wire or when a wire moves between the poles of a magnet (electromagnetic induction).