Magnetism

• 1. The split-ring commutator swaps the positive and negative connections every half turn.
  2. Therefore, the direction of the current through the coil reverses every half turn.
  3. This means that the forces acting on the coil will always be acting in the same direction.
  4. This causes the coil to rotate continuously in one direction.
• To increase the speed of an electric motor you can add more turns to the coil, use stronger magnets, or increase the current in the coil. 
• Current flows from north to south
• The closer together the magnetic field lines, the stronger the point on the magnet
• iron nickel and cobalt are magnetic
• Induced magnetism is when a magnetic material temporarily becomes a magnet when it's placed close to a permanent magnet
• Magnetic materials that gain and lose magnetism quickly are called magnetically soft materials.
• Magnetic materials that gain and lose magnetism slowly are called magnetically hard materials.
• An example of a magnetically soft material is iron.
• And example of a magnetically hard material is steel.
• A current carrying wire in the presence of a magnetic field will experience a force. This is called the motor effect.
• Speakers need an alternating current to function. 
• The magnetic field of the permanent magnet continually changes direction. 
• The coil is attracted to and then repelled to the magnets as the current changes direction (alternating current) because the magnetic field also changes direction. This produces a force on the cone. This causes the cone to vibrate and collide with particles in the air causing vibrations which are sound waves.