• When a?current?flows through a conducting wire a?magnetic field?is produced around the wire
• The shape and direction of the magnetic field can be investigated using plotting compasses

Diagram showing the magnetic field around a current-carrying wire

• The magnetic field is made up of?concentric circles
  • A circular field pattern indicates that the magnetic field around a current-carrying wire has?no poles

   

• As the distance from the wire increases the circles get further apart
  • This shows that the magnetic field is strongest closest to the wire and gets weaker as the distance from the wire increases

   

• The?right-hand thumb rule?can be used to work out the?direction?of the magnetic field

The right-hand thumb rule shows the direction of current flow through a wire and the direction of the magnetic field around the wire

• Reversing the direction in which the current flows through the wire will?reverse the direction?of the magnetic field

Side and top view of the current flowing through a wire and the magnetic field produced

• If there is?no current?flowing through the conductor there will be?no magnetic field
• Increasing the amount of current flowing through the wire will increase the strength of the magnetic field
  • This means the field lines will become?closer together

   

Factors Affecting Field Strength

• The strength of the magnetic fields field depends on:
  • The size of the current
  • The distance from the long straight conductor (such as a wire)

   

• A larger?current?will produce a larger?magnetic field?and vice versa
• The greater the?distance?from the conductor, the?weaker?the?magnetic field?and vice versa

The greater the current, the stronger the magnetic field. This is shown by more concentrated field lines