Electromagnetism

• What are the two ends of a magnet called?

  North pole and south pole
• Where are the magnetic forces strongest on a magnet?

  At the poles
• What happens when like poles of magnets are brought together?

  They repel each other
• What occurs when opposite poles of magnets are brought together?

  They attract each other
• What type of force is exerted between the poles of two magnets?

  Non-contact force
• Which materials are considered magnetic?

  Iron, cobalt, and nickel
• What is a permanent magnet?

  A magnet with its own magnetic field
• What is an induced magnet?

  A material that becomes magnetic in a field
• What happens to an induced magnet when removed from a magnetic field?

  It loses most of its magnetism
• How can a magnetic field be observed?

  Using a compass
• What determines the strength of a magnetic field?

  Proximity to the magnet
• Where is the magnetic field strongest in a magnet?

  At the poles
• What do magnetic field lines indicate?

  The direction of the magnetic force
• What does it mean when magnetic field lines are close together?

  The magnetic field is strongest
• How does the earth produce a magnetic field?

  Its core is made of iron
• What does a compass needle represent?

  The direction of the earth's magnetic field
• What happens when a current passes through a conducting wire?

  A circular magnetic field is produced

  
• What happens when the current is switched off in a wire?

  The magnetism is lost
• How can the strength of a magnetic field be increased around a wire?

  By increasing the current
• What effect does coiling the wire have on the magnetic field?

  It increases the strength of the field
• What are the methods to increase the strength of a magnetic field around a solenoid?

  • Add an iron core
  • Increase the number of coils
  • Increase the current passing through the wire
• What is an electromagnet?

  A solenoid with an iron core
• What are some applications of electromagnets?

  Electric motors and loudspeakers
• How can a magnetic compass be used to plot magnetic field lines around a magnet?

  1. Place the magnet on paper.
  2. Use a compass to mark directions.
  3. Draw dots at compass needle ends.
  4. Repeat for several positions.
  5. Join arrows to complete field lines.

  
• What causes the wire in an electric motor to rotate?

  The motor effect acting on the wire
• What happens to the force on the coil when it reaches a vertical position?

  The force becomes zero
• What is the purpose of a split ring commutator in an electric motor?

  To change the direction of current
• What does Fleming's left-hand rule help determine?

  The direction of the force produced
• What do the fingers of your left hand represent in Fleming's left-hand rule?

  Force, magnetic field, and current

  
• What is the equation for calculating the force produced by the motor effect?

  Force = magnetic flux density × current × length
• If a current of 8A flows through a wire that is 75cm long in a magnetic field of 0.5T, what is the force produced?

  3N
• What happens if the current is parallel to the magnetic field?

  No force is produced
• What is the relationship between the current and the magnetic flux density in producing force?

  Increased current increases the force
• What is the significance of the right angle in Fleming's left-hand rule?

  It indicates the orientation of forces
• What does the thumb represent in Fleming's left-hand rule?

  The direction of the force
• What does the index finger represent in Fleming's left-hand rule?

  The direction of the magnetic field
• What does the middle finger represent in Fleming's left-hand rule?

  The direction of the current