electromagnets

• North poles attract south poles
• A magnet has two poles: a north pole and a south pole
• South poles attract north poles
• South poles repel south poles
• North poles repel north poles
• Magnetic materials will experience a magnetic force when placed near a magnet, which is a type of non-contact force
• The three magnetic metals are iron, nickel, and cobalt
• A magnetic field is an area where a magnetic material will experience a force
• A permanent magnet will have its own magnetic field
• Magnetic field lines represent the field, traveling out of the north pole of the magnet and into the south pole
• The closer together the magnetic field lines are, the stronger the magnetic field will be
• We can find out the shape of a magnetic field using plotting compasses or iron filings
• The Earth has its own magnetic field, acting like a giant bar magnet inside the center of the Earth
• Electric Bells
• The electromagnet attracts the iron armature
• When it moves, it breaks the circuit, no longer allowing current to flow
• The coil and core are no longer magnetic, so the spring is no longer attracted and returns to its original position
• The bell is rung once, and the circuit is complete again, restarting the process
• Circuit breakers
• Circuit breakers detect large changes in current in a house and will break a circuit
• When a large current flows, the electromagnet becomes strong enough to attract an iron catch, breaking the circuit
• They can then be reset and used again, making them suitable as an electrical safety device in a home
• Loudspeakers
• Loudspeakers use an electromagnet to generate sound
• A current passes through the coil, creating an electromagnet that repels another permanent magnet, moving the cone in and out to create sound
• Using electromagnets
• Electromagnets are made by wrapping a coil of wire around a magnetic core
• Electromagnets only work when electricity is flowing through the coil, allowing them to be turned on and off
• Electromagnets are stronger than permanent magnets and produce the same magnetic field shape as a bar magnet
• You can increase the strength of an electromagnet by:

  • Increasing the number of turns on the coil around the core
  • Increasing the current flowing through the wire coil
  • Using a more magnetic material for the core, such as iron instead of aluminum