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S-72 Students will investigate the properties of electricity and magnetism? • What is a magnet? • What are the two poles called? Chapter 21 Magnetism SPS10 Students will investigate the properties of electricity and magnetism. c. Investigate applications of magnetism and/or its relationship to the movement of electrical charge as it relates to - electromagnets - simple motors - permanent magnets 21.1 Magnets and Magnetics Fields How do magnetic poles interact? How can a magnetic field affect a magnet that enters the field? Why are some materials magnetic while others are not? 21.1 Magnets and Mag Fields How do magnetic poles interact? • Magnetic force – the push or pull a magnet exerts on – Another magnet – On iron or a similar metal – On moving charges 21.1 Magnets and Mag Fields How do magnetic poles interact? • Magnets have two poles – North and south – Like poles repel – Opposite poles attract 21.1 Magnets and Mag Fields How can a magnetic field affect a magnet that enters the field? • Magnetic field – an area around a magnet that will attract or repel other magnets – – – – Begin at the north pole End at the south pole Can be seen using iron dust Arrows point in the direction of force on a north pole – The earth has a magnetic field 21.1 Magnets and Mag Fields Why are some materials magnetic while others are not? • Magnetic fields are cause by spinning electrons – Most of the time magnets are paired, and the fields cancel out – Magnetic domain – a region that has a large number of electrons with fields in the same direction – Magnetized – most of the domains are pointed in the same direction S-73 Doin’ The Happy Test Day Dance S-74 What does an electron do to create a magnetic field? What is a domain? What must happen to the domains in a substance for it to be a magnet? 21.2 Electromagnetism How can an electric charge create a magnetic field? How is an electromagnet controlled? How does an electric motors work? 21.2 Electromagnetism How can an electric charge create a magnetic field? • Electricity and magnetism are two faces of the electromagnetic force. – Electric force from charged particles – Magnetic force caused by spinning of charged particles 21.2 Electromagnetism How can an electric charge create a magnetic field? • Magnetic fields are formed by moving electric charges (Hans Christian Oersted) – If the charge moves down a wire, the magnetic field circles the wire 21.2 Electromagnetism How can an electric charge create a magnetic field? • Magnetic fields will put a force on a current carrying wire – These ideas are used to build • Electromagnets • Electric motors • Electric generators 21.2 Electromagnetism How is an electromagnet controlled? • Solenoid – a coil of current carrying wire that produces a magnetic field – A ferromagnetic rod inside a solenoid will increase the field strength – This is an electromagnet 21.2 Electromagnetism How is an electromagnet controlled? • The strength of an electromagnet can be controlled by – Changing the current – Changing the number of loops – Changing the type of core 21.2 Electromagnetism How does an electric motor work? • Electric motor – Electricity produces an electromagnet – The electromagnet is attracted or repelled by another magnet – A commutator ring changes the poles as after ½ a spin S-75 What is needed to make an electromagnet work? S-76 Using the right hand rule, what is the direction of the magnetic field around a wire if the current is traveling upward? 21.3 Electrical Energy Generation How does a generator work? What are some sources of electrical energy in the United States? 21.3 Electrical Energy Gen. How does a generator work? • Electromagnetic Induction – producing a current by – Moving an electrical conductor in a magnetic field – As simple as running a magnet through a coil – The faster the movement the higher the current – Current stops when the motion stops 21.3 Electrical Energy Gen. How does a generator work? • Generator – converts mechanical energy to electrical energy – Movement to current – Rotates a coil in a magnetic field – Power plants produce AC current 21.3 Electrical Energy Gen. How does a generator work? • Generator Generator Simulation – Loops of wire are spun – Whatever runs the power plant spins the wire – Every half spin the direction of current changes – Takes about 3300 watts to run a house 21.3 Electrical Energy Gen. What are some sources of electrical energy in the United States? • Sources of energy in the US – – – – – – 49.8% 19.9% 17.9% 6.5% 3% 2.3% Coal Nuclear Natural Gas Hydroelectric Petroleum Wind, Solar, Geothermal, Biomass S-77 What is electromagnetic induction? What kind of current does it produce? S-78 A. What is the direction of the magnetic field around the wire (arrow points the direction of the current) B. Draw the field around the magnet below. N S S-79 Test Day! Happy, Happy! Merry, Merry!