Electromagnets

• What happens when a current flows through a conducting wire?

  A magnetic field is produced around the wire.
• How do we prove there is a magnetic field around a wire?

  By using a compass. When the current is turned off, the compass needle lines up with the Earths magnetic field. However, if we turn the current on, the compass needle deflects which proves there is a magnetic field around the wire.
• What does the strength of the magnetic field depend on?

  The size of the current, a larger current produces a stronger magnetic field. It is also strongest when it is closer to the wire, the further from the wire, the weaker the magnetic field gets.
• What happens when we change the direction of the current?

  We change the direction of the magnetic field, a compass placed by this wire would deflect in the opposite direction to before.
• How do we work out the direction of the magnetic field produced by a wire?

  Right-hand grip rule
• How else do we increase the strength of the magnetic field?

  By coiling the wire, this shape is called a solenoid. When we turn on the current, we get a strong and uniform magnetic field inside the solenoid. The magnetic filed around a solenoid has a similar shape to the magnetic field around a bar magnet.
• What are the three ways we can increase the strength of the magnetic field produced by a solenoid?

  Increase the size of the current.

  Increase the number of turns of the coil.

  Place a piece of iron inside the solenoid (iron core).
• What is a solenoid containing an iron core called?

  Electromagnet, these are useful as we can change the strength of the magnetic field by changing the size of the current. They can also be turned on and off.