Transformers: Magnetism and electromagnetism: Physics: GCSE (9:1)

• Transformer


  A device that can increases or decreases the potential difference (voltage) of an alternating current
• Step-up transformer


  Increases the potential difference by having more turns on the secondary coil

  
• Step-down transformer


  Decreases the potential difference by having fewer turns on the secondary coil

  
• Structure of a basic transformer

  Consists of a primary coil and a secondary coil wound on an iron core

  
• Why iron is used for the core of a transformer


  Iron is easily magnetised and demagnetised
• Why transformers are supplied with alternating current

  So that magnetic field produced in the primary coil is continually changing
• Vp/Vs = np/ns


  The equation linking the ratio of the potential differences to the ratio of the number of turns on each coil

  
• Vp

  The symbol for potential difference across the primary coil

  
• Vs

  The symbol for potential difference across the secondary coil

  
• np


  The symbol for number of turns on the primary coil

  
• ns


  The symbol for number of turns on the secondary coil

  
• Volts (V)


  The SI unit for potential difference (voltage)

  
• VpIp = VsIs


  The equation linking the electrical power output and the electrical power input for transformers that are 100% efficient

  
• Ip


  The symbol for current in the primary coil

  
• Is


  The symbol for current in the secondary coil

  
• Amps (A)


  The SI unit for current