Electromagnets

• What is produced around a current-carrying wire

  A magnetic field is produced around the wire

  
• Magnetic field around a current-carrying wire

  Concentric circles coming out from the wire

  
• Direction of the magnetic field around a current-carrying wire

  Found using the right-hand grip rule

  
• Right-hand grip rule


  Thumb shows the the direction of conventional current and fingers show the direction of the field

  
• Effect of current on the strength of a wire's magnetic field


  The greater the current, the stronger the magnetic field
• Effect of distance on the strength of a wire's magnetic field


  The greater the distance from the wire, the stronger the magnetic field

  
• Solenoid


  Consists of a wire coiled up into a spiral shape

  
• Magnetic field around a solenoid

  Similar shape to that of a bar magnet

  
• Magnetic field inside a solenoid

  Strong and uniform

  
• Effect of current on the strength of a solenoid's magnetic field

  The greater the current, the stronger the magnetic field
• Effect of number of turns on the strength of a solenoid's magnetic field

  The greater the number of turns, the stronger the magnetic field
• Effect of core material on the strength of a solenoid's magnetic field

  Adding an iron core increases the strength of the magnetic field of a solenoid

  
• Electromagnet


  A solenoid with an iron core

  
• Advantages of electromagnets over permanent magnets

  An electromagnet can be switched on or off and its strength can be changed