Induced Potential, Transformers & the National Grid

• What is the generator effect?

  The generator effect is when motion is used to create electricity.
• How is a potential difference induced in a conductor?

  A potential difference is induced if an electrical conductor moves relative to a magnetic field or if there is a change in the magnetic field around a conductor.

  
• What happens when a wire cuts through magnetic field lines?

  When a wire cuts through magnetic field lines, a potential difference is induced in the wire.

  
• What factors affect the induced potential difference?

  The factors include the speed of movement, number of turns on the coils, size of the coils, and strength of the magnetic field.

  
• How does increasing the speed of the conductor affect the induced potential difference?

  Increasing the speed will increase the rate at which the magnetic field lines are cut, thus increasing the induced potential difference.
• What is the effect of increasing the number of turns on the coils of wire?

  Increasing the number of turns on the coils will increase the potential difference induced.

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

  Increasing the area of the coils will increase the potential difference induced because there will be more wire to cut through the magnetic field lines.

  
• What happens to the induced potential difference when the strength of the magnetic field is increased?

  Increasing the strength of the magnetic field will increase the potential difference induced.
• How does the orientation of the poles of the magnet affect the induced potential difference?

  The orientation of the poles of the magnet determines the direction of the induced potential difference.
• What will happen to the voltmeter reading when a magnet is stationary in the center of the coil?

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

  There is no relative movement between the coil and the magnetic field, so no magnetic field lines are being cut.
• What does Lenz's Law state?

  Lenz's Law states that the direction of an induced potential difference always opposes the change that produces it.
• What happens when a magnet is pushed north end first into a coil of wire?

  The end of the coil closest to the magnet will become a north pole, repelling the north pole of the magnet.

  
• What are the applications of the generator effect?

  • Generate alternating current (a.c.) in an alternator
  • Generate direct current (d.c.) in a dynamo
• What occurs when a magnet is pulled away from the coil of wire?

  The end of the coil closest to the magnet will become a south pole, attracting the north pole of the magnet.

  
• What is the structure of a simple alternator?

  • Rotating coil of wire
  • Permanent magnet
  • Slip rings
  • Carbon brushes

  
• What is the operation of an alternator?

  • A rectangular coil rotates in a uniform magnetic field.
  • The induced potential difference (p.d.) is measured.
  • The p.d. changes direction, producing alternating current.
• How does a dynamo operate?

  • The coil rotates, cutting through field lines.
  • A potential difference is induced.
  • The split ring commutator maintains current direction.
• What is the structure of a simple dynamo?

  • Rotating coil in a magnetic field
  • Permanent magnet
  • Split ring commutator
  • Carbon brushes

  
• What is the function of a bicycle dynamo?

  • Supplies electricity to bicycle lights.
  • Consists of a rotating magnet inside a coil.
  • Produces alternating current (a.c.) due to changing magnetic field direction.

  
• What is the shape of the potential difference graph for an alternator starting from a horizontal position?

  The graph is a cosine curve when starting from a horizontal position.

  
• What is the shape of the potential difference graph for an alternator starting from a vertical position?

  The graph is a sine curve when starting from a vertical position.
• When is the maximum potential difference induced in an alternator?

  A maximum potential difference is induced when the coil is horizontal and moving perpendicular to the magnetic field.
• When is no potential difference induced in an alternator?

  No potential difference is induced when the coil is vertical and moving parallel to the magnetic field.
• What is the shape of the potential difference graph for an alternator when it starts from a horizontal position?

  Cosine curve
• How does the starting position of the coil affect the shape of the potential difference graph for an alternator?

  The shape is a cosine curve if starting horizontally and a sine curve if starting vertically

  
• What is the induced potential difference when the coil is vertical at 0°?

  Zero
• What happens to the induced potential difference when the coil rotates by 90°?

  It reaches a maximum as the coil moves perpendicular to the magnetic field

  
• What is the induced potential difference when the coil has rotated by 180°?

  Zero
• What occurs when the coil has rotated by 270°?

  The induced potential difference is at a maximum and in the opposite direction to its position at 90°
• What is the induced potential difference when the coil completes a full 360° rotation?

  Zero
• What is the shape of the potential difference graph for a dynamo?

  Sine curve
• How does the induced potential difference behave when the coil is vertical at 0° in a dynamo?

  It is zero as the coil moves parallel to the magnetic field

  
• What happens when the coil has rotated by 90° in a dynamo?

  The induced potential difference is at a maximum as it moves perpendicular to the magnetic field

  
• What is the induced potential difference when the coil has rotated by 180° in a dynamo?

  Zero
• What occurs when the coil has rotated by 270° in a dynamo?

  The induced potential difference is at a maximum and in the same direction as its position at 90°
• What is the induced potential difference when the coil completes a full 360° rotation in a dynamo?

  Zero
• What factors can increase the magnitude of the induced potential difference in an alternator or dynamo?

  • Increasing the frequency of rotation of the coil
  • Increasing the number of turns on the coil
  • Increasing the strength of the magnet
  • Inserting a soft iron core into the coil
• What is the primary function of a transformer?

  To change the value of an alternating potential difference or current
• What are the main components of a basic transformer?

  • Primary coil
  • Secondary coil
  • Iron core