Magnetic fields around an electric current

• Entry Level Certificate
• Learning objectives


  • Draw the magnetic field around a current-carrying wire
  • Factors affecting the strength of the magnetic field around the wire
  • What a solenoid is
• When an electric current flows through a wire


  It produces a magnetic field around the wire
• Magnetic field lines


  Are circular around a wire
• The magnetic field pattern is a series of circles centred on the wire
• Factors affecting the strength of the magnetic field around a wire

  • Current
  • Distance from the wire
• Increasing the current


  Increases the strength of the magnetic field around the wire
• Increasing the distance from the wire

  Decreases the strength of the magnetic field
• Solenoid


  A long coil of insulated wire
• Coiling increases the strength of the magnetic field around a wire
• Electromagnet


  A solenoid with an iron core
• A solenoid's magnetic field pattern looks the same as that of a bar magnet
• Strength of the magnetic field around a wire

  • Depends on the current
  • Depends on the distance from the wire
• Adding an iron core increases the magnetic field strength of a solenoid
• Magnetic field


  Produced around the wire when a current flows through it
• Increasing the current in a wire

  Increases the strength of the magnetic field
• Decreasing the distance from a wire

  Increases the strength of the magnetic field
• Decreasing the current in a wire

  Decreases the strength of the magnetic field
• Solenoids are often used when a strong magnetic field needs to be produced
• The magnetic field direction is reversed if the current in the coil is reversed
• Current


  The flow of electric charge
• Distance


  The space between the wire and the point of measurement
• Magnetic field


  The area around a magnet or current-carrying wire where magnetic forces can be detected