Magnetism and Electromagnetism.

• When two magnets are brought together, they attract or repel depending on their poles.
• opposite poles

  attract
• like poles

  repel
• Define magnetic field

  the area around a magnet that a magnetic material or magnet can experience a force.
• magnetic materials can be attracted to

  magnets.
• Define Permanent Magnet.

  a magnet that produces its own magnetic field. It can attract or repel and has a North and South poles.
• Define Induced Magnet.

  Magnetic materials that become a magnet when placed inside the magnetic field of another magnet. Can only repel.
• What are the four magnetic materials.


  Iron, nickel, cobalt and steel.
• True or False: iron will hang onto its magnetism when taken off a magnet.

  false.
• Steel usually forms a permanent magnet that keeps its magnetism when moved away from a magnetic source.
• What type of magnet would you use to hold a picture on a fridge door?

  Permanent magnet because it needs to stay magnetic all the time (without electricity).
• Induced magnets always cause a force of what?

  attraction. Can never be repelled.
• How can you use the right hand grip rule to find the direction of a electromagnet field?


  Point your right thumb in the direction of conventional current (positive to negative), your fingers will curl in the direction of the magnetic field.
• What is a solenoid?

  a wire that is wound into a coil.
• How is the magnetic field in a solenoid created?

  A current passes through it. The magnetic field around a solenoid is stronger than round a straight wire, has a similar shape to bar magnet magnetic field. Magnetic field inside a solenoid is strong and uniform (same all the way through).
• What is an electromagnet?


  A solenoid wound around an iron core.
• How can an electromagnet magnetic field be increased?

  By the iron core, increasing the current or increasing the number of wire turns on the solenoid.
• Are electromagnets a type of permanent magnet?

  No, they can be switched on and off depending if current is flowing through it.
• What shape is the magnetic field round a straight wire like?

  concentric circles.
• What does a solenoid act as?

  a permanent magnet that produces it own magnetic field. The difference is that it can be switched off.
• Why would steel be a bad core for a solenoid?

  it is an alloy so will retain its magnetism after the current is switched off.
• What can be used as a core for a solenoid?

  A soft iron core will loose its magnetism once current stops flowing.
• What are the main points for a solenoid?

  Current flowing causes solenoid to produce a magnetic field somewhere in the device. The magnetic field can attract an object made of iron, nickel or cobalt, making part of the device move.
• How does an electromagnet work in an electric bell?

  When switch is pressed, current flows. Electromagnet will produce a magnetic field causing the armature to be attracted towards it. This will separate the contacts so current stop and armature will move back up. Now the contacts are close so current flows again and it repeats, continuously ringing bell.
• How does an electromagnet work in a circuit breaker?

  When a current gets too high, electromagnet will produce a magnetic field and attracts the armature. The spring will pull the contact up; as both won't be touching anymore the current will stop. The reset button can be pushed to put contact back down to normal.
• How does an electromagnet work in a relay switch?

  Switch is pressed on the safer circuit (one with lower voltage). Solenoid produces a magnetic field that attracts iron rocker. This pushes the pivot towards the contact on the second circuit. This acts a switch for the sencond circuit so the current will flow through it.
• Why is a relay switch used?

  when you need to switch on a circuit with a high voltage but don't want to get electrocuted so instead click a switch on a safer circuit.
• What do electric bells, circuit breakers and relay switches all use?

  electromagnets- solenoid.
• What is the circuit breaker an electromagnetic version of?

  a fuse.
• When a current carrying wire is placed into a magnetic field, it experiences a force. This is the motor effect and is due to the interaction of two magnetic fields.
• A magnetic field of concentric circles is created when a current flows through a conducting wire.
• How do you change the direction of the force produced (Flemings left hand rule)?


  Reverse direction of current.

  Reverse direction of magnetic field.

  If both are reversed, force will be in original direction.
• What is Flemings left hand rule?


  It helps us understand the direction of the generated force when a current carrying wire is placed into a magnetic field.
• How does Flemings left hand rule work?

  The thuMb represents Movement of the wire (Force- F), the Forefinger represents the direction of the magnetic Field (B) and the seCond finger represents the direction of Current (I). All fingers are mutually perependicular- at right angles to eachother.

  
• What do you call it if the wire moves away from you?

  into the page. Flemings left hand rule.
• What do you call it if the wire is moving towards you?

  out of the page. Flemings left hand rule.
• Which way does conventional current flow?

  From positive to negative. The longer line is positive.

  
• How do you calculate force of a wire in a motor effect?

  F= BIl (magnetic field strength x current x length of wire)
• What is force measured in?

  Newtons (N)
• What is magnetic field strength measured in?

  Teslas (T).