Transformers, motor effect, generator effect

• What is the motor effect?

  Force on a current-carrying wire in a magnetic field
• How is the motor effect utilized?

  In electric motors and loudspeakers
• What happens when a current-carrying wire is placed in a magnetic field?

  • The current interacts with the magnetic field
  • This interaction causes a force on the wire
  • The force is known as the motor effect
• When does the greatest force occur on a wire in a magnetic field?

  When the wire is perpendicular to the magnetic field
• When is there no force on a wire in a magnetic field?

  When the wire is parallel to the magnetic field
• What happens when the wire is at an angle between parallel and perpendicular?

  It experiences a smaller force
• What is the direction of the force in relation to the magnetic field and current?

  The force is always perpendicular to both
• What does Fleming's left-hand rule indicate?

  • Thumb: Direction of force
  • 1st finger: Direction of magnetic field
  • 2nd finger: Direction of current
• What do electric motors use to produce rotational motion?

  The motor effect
• How do loudspeakers convert electrical signals into sound?

  • Coil wrapped around a permanent magnet
  • AC flows through the coil
  • Magnetic field interaction creates force
  • Cone moves back and forth, producing sound
• What happens when AC flows through the coil in a loudspeaker?

  The coil moves due to magnetic field interaction
• How does reversing the current affect the loudspeaker's cone?

  It changes the direction of the force
• How is sound produced by the loudspeaker?

  Rapid movement of the cone creates sound waves
• What does the frequency of the sound produced match?

  The frequency of the AC current
• What is the generator effect?

  • Induction of current in a conductor
  • Occurs when moving relative to a magnetic field
  • Changes in magnetic field induce current
• What happens if the conductor is part of a full circuit during the generator effect?

  Current will flow
• What factors can reverse the induced current and potential difference (PD)?

  Reversing the magnet's polarity or direction
• What does continuous forward and backward motion of the magnet induce?

  AC potential difference and current
• What is AC?

  Current that changes direction over time
• What are the rules of the generator effect?

  • Induced current opposes the change that made it
  • Size of induced PD depends on rate of change of magnetic field
• How can the induced potential difference (PD) be increased?

  • Increase strength of magnetic field
  • Increase speed of conductor's movement
• What do alternators generate using the generator effect?

  Alternating current (AC)
• How do alternators work?

  • Coil rotates within a magnetic field
  • Direction of current changes every half rotation
  • Produces alternating current and potential difference
• What are slip rings used for in AC generation?

  • Allow current to reverse direction freely
  • Enable generation of alternating current
• What do dynamos do?

  • Rotating coil induces current within a magnetic field
  • Split-ring commutator ensures current flows in the same direction
• What type of current do dynamos generate?

  Direct current (DC)
• How do microphones work?

  • Convert sound waves into electrical signals
  • Magnet with coil of wire wrapped around
  • Diaphragm attached to the coil vibrates
  • Vibrations induce current, mirroring sound wave variations
• What are transformers used for?

  Changing voltage in electrical systems
• Why are transformers essential for the National Grid?

  They adjust voltage for electricity transmission
• What are the two types of coils in a transformer?

  Primary and secondary coils
• What does the primary coil in a transformer do?

  Handles the input voltage
• What is the function of the secondary coil in a transformer?

  Produces the output voltage
• What is a step-up transformer?

  Increases the output voltage
• How does a step-up transformer increase voltage?

  More turns on the secondary coil
• Why is high voltage used in the National Grid?

  Reduces current, minimizing energy loss
• What does a step-down transformer do?

  Decreases the output voltage
• How does a step-down transformer reduce voltage?

  More turns in the primary coil
• What is the equation for voltage in transformers?

  $\frac{V_p}{V_s} =$$\frac{n_p}{n_s}$
• What type of current do transformers work with?

  Alternating current (AC)
• Why do step-up transformers reduce energy loss?

  By lowering current through high voltage