Electricity and Magnetism

1. Electricity and Magnetism Unit 4

2. Electricity S8P5: Students will recognize characteristics of gravity, electricity, and magnetism as major forces acting in nature. B. Students will demonstrate the advantages and disadvantages of series and parallel circuits and how they transfer energy.

3. Electric Charge • All matter is made up of very small particles called atoms. • What are the 2 types of charged particles in atoms? • 1. Protons- positively charged particles • 2. Electrons- negatively charged particles

4. p Parts of an Atom • PROTONS • Each element on the Periodic Table has a different number of protons. • Protons have a positive charge • Found within the nucleus of the atom • Change the number of protons  change element

5. e- Parts of an Atom • ELECTRONS • An element on the Periodic Table has the same number of electrons and protons. • Electrons have a negative charge • Found outside the nucleus in the electronclouds • Change the number of electrons  ionize the element (give it a charge)

6. n Parts of an Atom • NEUTRONS • Most elements also have neutrons (except for Hydrogen) • Neutrons have no charge (neutral) • Found in the nucleus of the atom

7. The Law of Electric Charges • Law of Electric Charges: like charges repel and opposite charges attract

8. Charges • Like charges repel

9. Charges • Opposite charges attract

10. Electric Force and Electric Field • Electric Force: the force of attraction or repulsion on a charged particle that is due to an electric field • The greater the amount of charge, the greater the electric force. • The closer the charges are, the greater the electric force. • Electric Field: the space around a charged object in which another charged object experiences an electric force

11. Three Ways to Charge an Object • Friction: Charging by friction happens when electrons are “wiped” from one object onto another. • Conduction: Charging by conduction happens when electrons move from one object to another by direct contact. • Induction: Charging by induction happens when charges in an uncharged object are rearranged without direct contact with a charged object.

12. Electrical Potential Energy • Electrical charges can be stored on or in objects as potential energy. • Examples: • Electricity in a battery • Rubbing your socks on carpet • Electricity in clouds

13. Static Electricity • Static Electricity • the accumulation of electric charges on an object that are at rest • generally produced by friction or induction • When something is static, it is not moving. • 3 examples of Static Electricity • Clothes from a dryer sticking together • Balloon sticking to clothes after rubbing it on your hair • Negative charges on the bottom of a cloud during a thunderstorm

14. Electric Discharge • Electric discharge: the releaseof static electricity as charges move off an object • 2 examples of electric discharge: • 1. Walking across carpet and touching a metal doorknob • 2. Lightning

15. Electrical Kinetic Energy • Electricity • electrical energy due to the flow of electrons • Electric current • the rate at which electric charges pass through a given point (the rate that electrons flow) • The greater the flow of charge, the higher the current. • Electrons move from negative to positive. • Electric charges will always flow from a region of higher potential energy to a region of lower potential energy. • The difference in potential energy between two locations is known as potential difference (voltage).

16. Electrical Conductors • Electrical conductor: • a material in which electrons can move through easily • Electrons (e-) are loosely held • Examples: Most metals (copper, aluminum, and mercury)

17. Electrical Insulators • Electrical insulator • a material in which electrons are not able to move easily • Electrons (e-) are tightly held • Examples: Plastic, rubber, glass, wood, and air

18. DC and AC • 2 types of electric currents: • DC: direct current • AC: alternating current • In a direct current, the charges always flow in the same direction (one way). • Ex. Dry cell battery • In an alternating current, the charges continually shift from flowing in one direction to the reverse direction at regular intervals (two ways). • Ex. Electrical outlets

19. Voltage • Voltage • the push or force that causes electrons to move from negative to positive • a measure of how much work is needed to move a charge between two points • The size of the current depends on the voltage. • The greater the voltage, the greater the current. • A greater current means that more charges move in the wire each second.

20. Copper - low resistance Tungsten - high resistance Resistance • Resistance • a measure of how difficult it is for electrons to move through a material • electrical energy is converted to thermal energy and light (Ex.: a light bulb) • You can think of resistance as “electricalfriction.” • A resistor is an object that is added to a circuit that restricts the flow of electrical energy. • An object’s resistance depends on its material, thickness, length, and temperature. • Good conductors, such as copper, have a low resistance. However, poor conductors, such as Tungsten, have a higher resistance.

21. Cells • Batteries are chemical cells. • Batteries convert chemical energy into electricity. • A battery can provide the voltage (push) that is needed to keep current flowing in a circuit. • Electric charges are repelled by the negative terminal and attracted toward the positive terminal. • Photocells are devices that convert light energy into electrical energy. • Ex. Solar panels

22. Electric Circuits:Parts of an Electric Circuit • What is a circuit? -a complete, closed path through which electric charges flow • Just like a roller coaster, an electric circuit forms a loop; it begins and ends in the same place. • All circuits need 3 basic parts. 1. Energy source- provides energy to the circuit; can be a battery, a photocell, or an electric generator at a power plant 2. Wires- connect the other parts of a circuit; made of conducting materials that have low resistance, such as copper 3. Loads- change electrical energy into other forms of energy; examples include light bulbs, appliances, televisions, and electric motors

23. A Switch to Control a Circuit • A switch is used to open and close a circuit. • In order for loads (like the lights in this classroom) to work, the switch needs to be closed to allow charges to flow through. • If a switch is open, the load will not work.

24. Types of Circuits • What are the 2 types of circuits? • Seriescircuits • Parallelcircuits

25. Series Circuit • Series Circuit: • a circuit in which all the parts are connected in a single loop • only one (single) path for charges to follow; so, the charges moving through this circuit must flow through each part of the circuit.

26. Series Circuits: Advantages and Disadvantages • Advantages: • The bulbs and batteries will last longer. • Use less power • The current is the same throughout the circuit; therefore, lights shine with equal brightness. • Disadvantages • Lights get dimmer as more lights are added. • Each device (light bulb, etc.) receives a fraction of the total voltage. • Adding more bulbs resistance goes up, current goes down, and bulbs get dimmer • Only one path for charges to flow. • A break in a series circuit causes charges to stop flowing; if one light in a series circuit goes out, the other lights go out, too.

27. Parallel Circuit • Parallel circuit – a circuit that has more than one path for the flow of electricity because the parts are joined in branches or multiple loops

28. Parallel Circuits: Advantages and Disadvantages • Advantages: • The voltage (potential difference) across each part is the same. • Each bulb will glow at full brightness regardless of the number of bulbs. • There are multiple paths for charges to travel. • If one bulb breaks, the other bulbs will still work. • Disadvantages: • The bulbs and batteries will die faster. • Use more power • The current is not the same in the circuits • current takes path of least resistance

29. Household Circuits • Combination of parallel circuits • too many devices can cause wires to overheat • Safety Features: • fuse - metal melts, breaking the circuit • circuit breaker - bimetallic strip bends when hot, breaking the circuit

30. Magnetism and Electromagnetism S8P5. Students will recognize characteristics of gravity, electricity, and magnetism as major kinds of forces acting in nature. c. Investigate and explain that electric currents and magnets can exert force on each other.

31. Magnetism • Magnetism • The properties and interactions of magnets • Due to the arrangement of electrons • Closely related to electricity

32. Magnetic Force • Magnetic Force • Force of attraction or repulsion generated by moving or spinning electric charges • Increases as magnets move closer together and decreases as magnets move farther apart

33. Magnetic Poles • Magnetic Poles • Regions on a magnet where the magnetic force exerted by a magnet is the strongest • Like poles repel. • Opposite poles attract. • A broken magnet creates new poles.

34. Magnetic Field • Magnetic Field • Area around a magnet where magnetic forces act • Magnetic field lines show the direction of the field (NS) • Molecular Expressions: Electricity and Magnetism - Interactive Java Tutorials: Magnetic Field Lines

35. Earth’s Magnetic Field • Earth’s inner core is made of a solid ball of iron and nickel surrounded by a liquid layer of molten iron and nickel. • The circulation of the molten iron and nickel in the Earth’s outer core produces a magnetic field. • Therefore, Earth acts like a giant bar magnet.

36. Compass • A compass needle is a small bar magnet with a north pole and a south pole. • The needle aligns with the magnetic field lines of the Earth.

37. Earth’s Magnetic Poles • A compass’ needle points to the north geographic pole due to the south magnetic pole being nearby. • Magnetic poles are NOT aligned with geographic poles. They also shift and flip.

38. Magnetic Domains • Magnetic Domains • Groups of atoms with aligned magnetic poles • Like tiny magnets of different sizes domain • In a magnetized object, the domains are all aligned. • In a non-magnetized object, the domains are not aligned and cancel each other out.

39. Magnetic Materials • Few metals such as iron, cobalt, and nickel are attracted to magnets or can be made into permanent magnets. 69

40. Types of Magnets • Ferromagnets: magnets made of iron, nickel, cobalt, or mixtures of these metals (ex. magnetite) • Electromagnets: magnets formed when current passes through a coil of wire (solenoid) surrounding an iron core

41. Permanent Magnets • Permanent Magnets • Magnets that keep their magnetism after they are removed from a magnetic field • Keep their magnetic properties longer than temporary magnets • Some are made of alnico: an alloy of aluminum, nickel, cobalt, and iron.

42. Permanent Magnets • Permanent magnets can be made: • Place a magnetic material (iron, cobalt, or nickel) in a strong magnetic field. • This causes the magnetic domains in the material to line up. • This creates a strong magnetic field inside the material which keeps the domains in alignment. • Can be heated or dropped to demagnetize

43. Temporary Magnets • Temporary Magnets • Magnets made from materials that are easy to magnetize • Tend to lose their magnetism easily • Ex. Soft iron items like paperclips and nails

44. Magnetism in Nature aurora borealis • Auroras • They are formed when charged particles from the sun (known as solar wind) hit oxygen and nitrogen atoms in the air. The atoms become excited and then give off many colors of light. • The charged particles can crash into the atmosphere at and near the magnetic poles. • North Pole • Northern lights: aurora borealis • South Pole • Southern lights: aurora australis aurora australis

45. Magnetism and Electricity • Moving charges, like those in an electric current, produce magnetic fields. • Around a current-carrying wire the magnetic field lines form circles.

46. Magnetism and Electricity • As the current in the wire increases, the strength of the magnetic field increases. • The direction of the magnetic field around the wire reverses when the direction of the current in the wire reverses.

47. Electromagnetism • Electromagnetism • The interaction between electricity and magnetism

48. Solenoids • Solenoid • A single wire wrapped into a cylindrical wire coil that produces a magnetic field when electricity passes through it. • If wrapped around an iron core, an electromagnet is formed.

49. Electromagnets • Electromagnet • A magnet formed when current passes through a coil of wire (solenoid) surrounding an iron core • The iron core becomes magnetized only when current flows through the wire.

50. Electromagnets • The strength of an electromagnet’s magnetic field can be increased by: • Adding more wraps of wire to the solenoid • Increasing the current passing through the wire by increasing the voltage. • Increasing the size of the iron core