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Electric motors

Electric motors. Activity 5. How an electric motor works. A coil of wire with a current produces a magnetic field. The coil then acts like a small magnet. When the coil is near a stronger magnet, the coil will move to align with the stronger magnet due to the force of the stronger magnet.

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Electric motors

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  1. Electric motors Activity 5

  2. How an electric motor works • A coil of wire with a current produces a magnetic field. • The coil then acts like a small magnet. • When the coil is near a stronger magnet, the coil will move to align with the stronger magnet due to the force of the stronger magnet. • In a motor, the current in the coil switches direction over and over again, so the coil keeps spinning as it tries to align with the magnetic field. http://www.youtube.com/watch?v=ziWUmIUcR2k (build a simple motor) http://www.youtube.com/watch?v=Q2mShGuG4RY (how it works) http://www.youtube.com/watch?v=1W1sbFALXEA (how it works)

  3. Inside a Motor Commutator

  4. Commutator

  5. Commutators and brushes • Commutator and Brushes on DC Motor • To keep the torque on a DC motor from reversing every time the coil moves through the plane perpendicular to the magnetic field, a split-ring device called a commutator is used to reverse the current at that point. The electrical contacts to the rotating ring are called "brushes" since copper brush contacts were used in early motors. Modern motors normally use spring-loaded carbon contacts, but the historical name for the contacts has persisted.

  6. Extending the discussion to sea perch • This simple motor is related to the motors that you will attach to your SeaPerch ROV. • If you opened a motor up, you would find coils of wire and magnets. • When the wires are connected to a power supply, the motors will spin.

  7. Extension activity • Take the motor you have built and turn the battery around • The current will run in the opposite direction through the loops of wire. • What happens to the direction in which the loop spins? • At times, you’ll want to put your SeaPerch in reverse – in next week’s activity, we’ll learn how to build a circuit where you can change the direction of the current.

  8. more cool extensions • Building a speaker out of paper cups, wires, and magnets: • http://cse.ssl.berkeley.edu/lessons/indiv/regan/speakerlab.html • http://www.exploratorium.edu/afterschool/activities/docs/cupspeaker.pdf • Explore the relationship between electric fields and magnetic fields. • Place a compass close to the wire. Connect the wire to a power supply and see that the compass needle is deflected. Change the position of the compass. Notice it is deflected in a different direction. • http://www.youtube.com/watch?v=BM4m2GId3F8&feature=fvst (Oersted’s Discovery) • http://www.youtube.com/watch?v=jCcUochTbVo (right hand rule)

  9. Source of Activity • http://www.phillyseaperch.org/learning-modules.html

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