Magnetism

• What is produced when current flows through a conducting wire?

  A magnetic field is produced around the wire.
• What determines the strength of the magnetic field around a current-carrying wire?

  The magnitude of the current and distance from the wire.
• What is a solenoid?

  A coil of wire creating a strong magnetic field.
• Describe the magnetic field found inside a solenoid.

  Strong and uniform.
• What is an electromagnet?

  A solenoid with an added iron core.
• How does adding an iron core affect an electromagnet?

  It increases the strength of the magnetic field.
• What is the motor effect?

  A force between a magnetic field and a current-carrying conductor.
• What rule is used to determine the force experienced due to the motor effect?

  Fleming’s Left-Hand Rule.
• What does the forefinger represent in Fleming’s left-hand rule?

  The direction of the magnetic field.
• What does the second finger represent in Fleming’s left-hand rule?

  The direction of current flow in the conductor.
• What factors affect the size of the force on a current-carrying wire in a magnetic field?

  The magnitude of the current and strength of the magnetic field.
• What happens to the force if the direction of current in a wire is reversed?

  The direction of the force is reversed.
• What happens to the force if the strength of the current is increased?

  The strength of the force is increased.
• What criteria must be met for the equation linking force, magnetic flux density, current, and length to hold?

  The conductor must be at right-angles to the magnetic field.
• What is the unit used for magnetic flux density?

  Tesla, T.
• How does an electric motor work?


  A coil in a magnetic field experiences forces causing rotation.
• How do loudspeakers make use of the motor effect?


  They convert current variations into sound pressure variations.
• Explain how a loudspeaker works.

  A cone vibrates due to current-induced magnetic field interaction.
• How is the pitch of the sound from a loudspeaker changed?

  By altering the frequency of the a.c current.