Electromagnetism

• What phenomenon does electromagnetism describe?

  Electric currents produce magnetic fields
• How does an electric current affect a wire?

  It produces a magnetic field around the wire
• What shape do the magnetic field lines take around a wire?

  Concentric circles around the wire
• Where is the magnetic field strongest around a wire?

  Closest to the wire
• What determines the direction of the magnetic field around a wire?

  The direction of the electric current
• What rule helps determine the direction of the magnetic field?

  The right hand rule
• How do you use the right hand rule for current flowing upwards?

  Thumb up, fingers curl anti-clockwise
• What happens to the magnetic field if the current direction is reversed?

  The magnetic field direction also reverses
• How does a flat circular coil affect magnetic fields compared to straight wires?

  It combines fields into a single magnetic field
• What is a solenoid?

  A coil of wire with many turns
• How does the magnetic field inside a solenoid compare to outside?

  Strong and uniform inside, weak outside
• What is an electromagnet?

  An induced magnet created by electric current
• What happens to an electromagnet when the current is turned off?

  The magnetic field disappears
• How can you reverse the direction of an electromagnet's magnetic field?

  By reversing the current direction
• What are the four ways to increase an electromagnet's strength?

  Increase current, turns, decrease length, add iron core
• Why does adding an iron core increase an electromagnet's strength?

  Iron becomes an induced magnet when current flows
• What happens to the iron core when the current is turned off?

  It loses its magnetic field
• What is a magnet?

  A material that produces a magnetic field
• What is the most common type of magnet?

  Bar magnets
• What do all magnets have in common?

  They have a north and a south pole
• How do we represent magnetic fields?

  Using field lines
• How do you draw field lines for a magnet?

  From the north pole to the south pole
• What is the process for drawing magnetic field lines?

  • Draw a straight line into the south pole
  • Draw a line coming out of the north pole
  • Add a pair of slightly curved lines into the south pole
  • Add a similar pair coming out of the north pole
  • Draw loops around from north to south
  • Ensure arrows point out of north and into south
• What does the density of field lines indicate?

  The strength of the magnetic field
• Where is the magnetic field strongest in relation to the poles?

  Near the north pole
• How can we find the poles of a magnet?

  Using a compass
• Why does a compass needle point towards the south pole of a magnet?

  Because it is a tiny bar magnet
• What happens when you push the north poles of two magnets together?

  They repel each other
• What creates the force of repulsion between two magnets?

  The interaction of their magnetic fields
• What occurs when opposite poles of magnets are brought together?

  They attract each other
• What are the key points about magnetic field lines?

  • Represent the direction of the magnetic field
  • Indicate the strength of the magnetic field
  • Drawn from north pole to south pole
  • Closer lines indicate stronger fields