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Lesson V “Electromagnetism”

Lesson V “Electromagnetism”. Matter & Energy. S.W.B.A.T. Explain how an electric charge creates a magnetic field Describe how electromagnets are used Relate electromagnets to everyday devices. Electricity & Magnetism.

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Lesson V “Electromagnetism”

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  1. Lesson V “Electromagnetism” Matter & Energy

  2. S.W.B.A.T. • Explain how an electric charge creates a magnetic field • Describe how electromagnets are used • Relate electromagnets to everyday devices

  3. Electricity & Magnetism • Along with gravity and the strong & weak nuclear force, electromagnetism makes up one of the four known forces in the universe • Electricity & magnetism are two parts of the same force

  4. Electricity & Magnetism • Hans Oersted(1820) discovered through experiments that electricity and magnetism were related • Oersted showed that electric current moving through a wire deflected a compass needle

  5. Electricity & Magnetism • Flowing electric charges create magnetic fields • Magnetic field lines form circles or loops around a flowing charge moving through a straight wire

  6. Electricity & Magnetism • Electric charges moving through a magnetic field will be shifted 90o from its direction of movement and from the magnetic field loop • If the current flow is reversed the charges will shift 90o in the opposite direction

  7. “Right-Hand Rule”

  8. Electricity & Magnetism • If the current is moving parallel with the magnetic field loop then there is no deflection • Electric fields are different than magnetic fields in that it exerts a force on a charge in the same or opposite direction (+ or – charge)

  9. Electromagnets • Looping a wire into a coil will create a combined magnetic field • A solenoid is created when a current is passed through the looped wire

  10. Electromagnets • An electromagnet is made when an iron core is placed inside the looped wire or solenoid • Electromagnets are very strong magnets that can change strength & direction with a change in current

  11. Electromagnets • Increasing the current will increase the electromagnet’s strength • Increasing the amount of wire loops in the solenoid will also increase electromagnetic strength

  12. Video (3:18) “Electromagnetism: Magnetic Force”

  13. Electromagnetic Devices • Electromagnetic devices include electric motors, galvanometers,loudspeakers and generators • Electric motorsuse electromagnets to turn an axle

  14. Electromagnetic Devices • Electric motors contain a central iron core that is wrapped by many loops of wire (solenoid) • As the current flows through the wires magnetic fields are created • The magnetic fields create a push & pull which forces the axle to turn

  15. How an Electric Motor Works

  16. Electromagnetic Devices • A galvanometer uses an electromagnet to measure small amounts of current • Galvanometers are used to gauge how much gasoline is left in a car & for laser guidance systems

  17. Electromagnetic Devices • Loudspeakers use a solenoid wrapped around one pole of a permanent magnet • Sound is reproduced as the changing current produces a change in magnetic fields

  18. Electromagnetic Devices • The magnetic force moves the solenoid back & forth causing a thin membrane to vibrate • These vibrations produce sound waves from the speaker which closely matches the original sound

  19. Electromagnetic Devices • Generators (AC & DC) convert mechanical energy to electrical energy • A rotating coil of wire (or solenoid) placed in a magnetic field will generate an electric charge

  20. Electromagnetic Devices • The electric charges are induced into a wire which then creates an electric flow • Generators resemble electric motors but generate electricity instead of using it (the opposite of electric motors!) Video (3:49) “World’s First Electric Generator”

  21. Class Activity • List three devices (not mentioned in this lesson) that use electromagnetic forces • Explain what each device does and how electricity & magnetism interact in the device

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