7.3 Induced Potential, Transformers & National Grid

• What is the generator effect?

  Motion creates electricity instead of electricity creating motion
• How is the generator effect defined?

  Movement relative to a magnetic field induces potential difference
• What happens if a conductor is part of a complete circuit during the generator effect?

  A current is induced in the conductor
• What occurs when a wire cuts through magnetic field lines?

  A potential difference is induced in the wire

  
• What induces a potential difference in a conductor?

  Relative movement between the conductor and magnetic field

  
• What happens when a conductor moves through a fixed magnetic field?

  The wire cuts through the field lines
• What occurs when a magnet moves through a coil?

  The field lines cut through the turns of the coil
• What can be used to measure the size of the induced potential difference?

  A sensitive voltmeter
• What factors affect the induced potential difference?

  Speed, number of turns, size, strength, orientation
• How does increasing the speed of movement affect the induced potential difference?

  It increases the induced potential difference
• What happens when the number of turns on the coils increases?

  The potential difference induced increases
• How does the size of the coils affect the induced potential difference?

  Increasing size increases the potential difference
• What effect does increasing the strength of the magnetic field have?

  It increases the potential difference induced
• How does the orientation of the poles of the magnet affect the induced potential difference?

  It determines the direction of the induced potential difference
• What does Lenz's Law state?

  Induced potential difference opposes the change that produces it
• What happens when a magnet is pushed into a coil of wire?

  The end of the coil closest becomes a north pole

  
• What occurs when the magnet is stationary in the center of the coil?

  There will be no deflection of the needle
• Why does the needle on the voltmeter not deflect when the magnet is stationary?

  There is no relative movement between the coil and magnetic field
• What should you state when discussing factors affecting induced potential difference?

  Add more turns to the coil
• What happens when a magnet is pulled away from the coil?

  The end of the coil closest becomes a south pole
• How does the coil react when the magnet is pulled away?

  It applies a force to oppose the magnet's movement
• What are the applications of the generator effect?

  • Generate a.c. in an alternator
  • Generate d.c. in a dynamo
• What is an alternator?

  A device that converts motion into electrical output
• What does a simple alternator consist of?

  A rotating coil between poles of a permanent magnet

  
• What is the function of slip rings in an alternator?

  To allow alternating current to flow to the external circuit
• How does the induced potential difference behave in an alternator?

  It constantly changes size and direction
• When is the maximum potential difference induced in an alternator?

  When the coil is horizontal and moving perpendicular to the field
• What is a dynamo?

  A device that converts electrical input into motion
• What component does a dynamo use instead of slip rings?

  A split-ring commutator
• How does the split-ring commutator function in a dynamo?

  It changes connections every half turn to maintain current direction
• What is the output of a bicycle dynamo?

  It produces alternating current (a.c.)
• What is the shape of the potential difference graph for an alternator?

  A sine or cosine curve
• When does the induced potential difference reach zero in an alternator?

  When the coil is vertical and moving parallel to the field
• What happens when the coil rotates by 90° in an alternator?

  The induced potential difference is at a maximum
• What occurs when the coil rotates by 180° in an alternator?

  The induced potential difference is zero again
• What happens when the coil rotates by 270° in an alternator?

  The induced potential difference is at a maximum again
• What shape does the graph of induced p.d. with angle for an alternator take?

  Sine curve
• What happens to the induced p.d. when the coil is vertical at 0°?

  The size of the induced p.d. is zero
• What is the position of the coil when the induced p.d. is at a maximum?

  When the coil is horizontal at 90°
• What happens to the induced p.d. when the coil rotates to 180°?

  The size of the induced p.d. is zero