Unit 1.9

• Motor


  • Can be made to spin
  • Spin faster by using a coil with more turns, larger current, stronger magnets, or larger coil area
  • Change direction by changing current direction or reversing field
• Motor operation

  1. Wire carrying current through magnetic field has force acting on it

  2. Direction of force given by Fleming's Left Hand Rule

  3. Size of force calculated using F=BIl
• Fleming's Left Hand Rule

  Thumb = Force/Motion, Middle finger = Current, First finger = Field, From N to S
• Generator operation

  1. Wire moved through magnetic field generates current

  2. Direction of force given by Fleming's Right Hand Rule

  3. Can create Alternating Current

  4. Larger current by using coil with more turns, stronger magnets, or larger coil area

  5. Faster turning increases current but also frequency
• Fleming's Right Hand Rule

  Thumb = Force/Motion, Middle finger = Current, First finger = Field, From N to S
• Magnetic field

  • Area where magnetic force is felt
  • Strength shown by closeness of lines
  • Wire carrying current creates magnetic field
  • Larger current creates stronger field, changing direction reverses field
  • More coil turns creates stronger field, changing current direction reverses field
• Transformer

  • Uses magnetic field to step up or step down voltage
  • Steps: 1) AC in primary coil creates alternating magnetic field, 2) Core strengthens and connects field to secondary coil, 3) Alternating field in secondary coil generates AC
• Transformer ratio

  V1/V2 = N1/N2 (where V1 is input voltage, V2 is output voltage, N1 is primary coil turns, N2 is secondary coil turns)