Electromagnetic Induction

• What happens when an electrical conductor moves relative to a magnetic field?

  A voltage (potential difference) is induced across the conductor.
• What happens to an electrical conductor when there is a change to the magnetic field that it is placed in?

  The voltage(potential difference) is also changed
• How do you produce an electric current using a magnet and a conductor on a small-scale?

  -By moving a coil of wire between magnetic poles or moving a magnet within a coil of wire.

  -Once a voltage is induced, if there is a complete circuit, a current will also be induced
• How is electrical current produced on a large scale?

  An electromagnet is rotated around a coil
• What factors affect the size of an induced voltage?

  -The numbers of turns on the coil of wire

  -How strong the magnetic field is

  -The speed of the movement
• What is the requirement for an induced potential difference to cause a current flow?

  The conductor must be part of a complete circuit.
• What can be said about the direction of the magnetic field produced by an induced current?

  -The direction of the field is such that it opposes the change that induced the current

  -This change is either the movement of the conductor or a change to the field
• What are two ways that the generator effect is used to generate different types of current?

  -In an alternator to produce alternating current

  -In a dynamo to produce a direct current
• How does a dynamo generate current?

  (electromagnetic induction) A coil of wire rotates inside a magnetic field. A split ring commutator is used to ensure it continues rotating in the same direction, therefore keeping the current flowing in the same direction(direct current)
• How is electromagnetic induction used in alternators to generate alternating current?

  A coil of wire rotates in a magnetic field. The end of this coil is connected to slip rings which will cause the current to change the direction while rotating. This means alternating current is produced
• How do loudspeakers make use of the motor effect?

  The motor effect is used to convert variations in the current of an electrical circuit into the pressure variations which produced audible sounds
• Explain how a loudspeaker works

  -A cone wrapped in wire is connected to an a.c power supply and is placed in a permanent magnetic field

  -When current flows through the wire, it creates a magnetic field which interacts with the permanent field

  -This produces a force which causes the cone to vibrate, producing sound
• What is induced potential?

  It is the potential difference created by movement.
• What is the generator effect?

  It is the induction of current in a circuit.
• What happens to the potential difference when the wire stops moving?

  The potential difference is lost.
• What occurs when the wire moves back down through the magnetic field?

  The potential difference is induced again, but reversed.
• What is the relationship between the direction of movement and the direction of current?

  The direction of current switches with movement direction.
• What happens to the current if the movement stops?

  The current also stops.
• How can an induced potential be created without moving the wire?

  By moving the magnetic field instead.
• What is required for the generator effect to occur?

  The wire must pass through the magnetic field.
• What happens if the wire moves along the magnetic field?

  No induced potential difference or current occurs.
• What factors affect the size of the induced potential difference?

  • Strength of the magnetic field
  • Speed of wire movement
  • Shape of the wire (coiling)
• How does a stronger magnetic field affect induced potential difference?

  It increases the induced potential difference.
• What effect does moving the wire more rapidly have on induced current?

  It increases the induced current.
• How does shaping the wire into a coil affect induced potential difference?

  More turns increase the induced potential difference.
• What happens when a magnet moves in and out of a coil of wire?

  An induced current is produced in the wire.
• What occurs to the direction of current when the direction of movement changes?

  The direction of current also changes.
• What happens to the induced current when the poles of the magnet are switched?

  The direction of the induced current switches.
• How does the induced current affect the movement of the magnet?

  • Induced current creates its own magnetic field
  • This magnetic field opposes the magnet's movement
  • Makes it harder to push or pull the magnet
• What happens when the North Pole of a magnet is inserted into a coil?

  The coil becomes a North Pole, repelling the magnet.
• What occurs when the North Pole is pulled out of the coil?

  The coil becomes a South Pole, attracting the magnet.
• What does the induced current do to the energy from the movement of the magnet?

  It transfers energy into the movement of the current.