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Motors Lesson 9

Motors Lesson 9. Thinking About Motors. What is a motor? Device that converts energy into mechanical motion What are motors used for? Hard drives, disk drives, fans, DVD players etc.. How do motors work?. Magnets- Necessary Component of Motors. History

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Motors Lesson 9

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  1. MotorsLesson 9

  2. Thinking About Motors • What is a motor? • Device that converts energy into mechanical motion • What are motors used for? • Hard drives, disk drives, fans, DVD players etc.. • How do motors work?

  3. Magnets- Necessary Component of Motors • History • Named for a region in Asia Minor called Magnesia • Magnesia was the first location magnetic rocks were found • Earliest Uses- 11th Century China • Compass needles • Needle is made of a magnet that points towards the north pole

  4. How Magnets Work • Magnets Attract • Metals: iron, nickel cobalt • Why? • Alignment of atomic structure of material

  5. Magnetic Poles • Magnets have two poles • North pole- attracts south pole, repels north • South pole- attracts north pole, repels south • Easy way to determine north vs. south pole • Hold a compass next to a magnet • The compass needle will point to the south pole

  6. Mechanical Motion from Electricity • Hans Christian Oersted • Discovered relationship in 1800’s between: • Mechanical Force • Magnetism • Electricity • Followed up by Maxwell, Farady and Lorentz

  7. Mechanical Motion from Electricity • Basis for Electric Motor • A wire conducting current will experience a force when it is placed in a magnetic field F = iL x B • F (Force) • i (Current) • L (Length of Conductor) • x (Cross Product) • B (Magnetic Field Strength)

  8. Mechanical Motion from Electricity • Vectors • Vectors represent a quantity with a size and direction • According to the formula: • The force is a cross product of the vectors B and iL • Cross Product: takes two vectors B and iL and produces a third: BiLsin(Ө) • We will only consider vectors at right angles: F= iLB

  9. Mechanical Motion from Electricity Right Hand Rule • Used to find the direction of the force on the wire • Point hand with open palm in direction of first vector in the cross product (iL) • Close fingers in the direction of second vector (B) • Your thumb is now pointing in direction of F

  10. Practice the Right Hand Rule!!!

  11. Inside a Motor • Force on current (i) in a magnetic field can be turned into torque • Simple: run current through a loop of wire in a magnetic field • Current switches direction based on what side of the loop it is on • Results in a pair of forces which cause torque • The loop will align with the magnets but will not spin

  12. How Does a Motor Spin? • Add physical components to make current change direction • Brushes: attached to power source, do not move • Commutator: attached to the coil , spins with coil • When commutator spins , brushes change direction which results in current switching direction • The torque will increase with more coils

  13. A Motor in Pieces

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