Electromagnets

• Entry Level Certificate
• Electromagnet


  A solenoid wrapped around an iron bar
• When a current is passed along a wire


  A magnetic field is created around the wire
• Because of this, the iron bar is magnetised
• When the current is switched off, the iron bar loses its magnetism
• Investigating electromagnets


  1. Take an iron bar and wrap insulated wire around it

  2. Connect the wires to a battery

  3. Use the electromagnet to pick up metal paperclips

  4. Count how many paperclips it can hold

  5. Record this number in a table

  6. Repeat five times to see a pattern

  7. Increase the number of coils and repeat
• Strength of an electromagnet can be increased by

  • Increasing the number of coils
  • Increasing the current in the coil
• Uses of electromagnets


  • Car scrapyard
  • Relay
• In a scrapyard, the crane has a large electromagnet attached
• When the electromagnet is switched on


  The crane picks up the cars
• When the crane has to drop the cars

  The electromagnet is switched off
• Relay


  An electrical switch that is opened and closed by another circuit
• Relay operation


  1. The first circuit contains an electromagnet

  2. When the electromagnet turns on, it attracts the iron armature

  3. This pushes the second switch closed

  4. When the first circuit is switched off, the electromagnet turns off and the iron armature is released
• An electromagnet is a solenoid wrapped around an iron bar
• Control variable


  A variable that is kept constant during an experiment
• The table and graph show the student's results
• The current in amps (A) and the number of paperclips are recorded
• How many paperclips were picked up when the current was 3 A?
• What pattern is shown by the student's results?
• What is one control variable in this experiment?