Topic 13: electromagnetic induction

• What determines the direction of the induced potential difference?

  The orientation of the poles of the magnet
• What does the induced potential difference always do in relation to the change that produces it?

  It always opposes the change that produces it
• What happens when a magnet is pushed north end first into a coil of wire?

  The end of the coil closest becomes a north pole
• Why does the end of the coil closest to the magnet become a north pole?

  Due to the generator effect and induced potential difference
• What occurs when a magnet is pulled away from the coil of wire?

  The end of the coil closest becomes a south pole
• What is the purpose of a transformer?

  To change the value of an alternating potential difference
• What are the main components of a basic transformer?

  • Primary coil
  • Secondary coil
  • Iron core
• Why is iron used in transformers?

  Because it is easily magnetised
• What happens to the current in wires when electricity is transmitted over large distances?

  The current heats the wires, causing energy loss
• How does increasing the potential difference affect current in power lines?

  It results in a smaller current being transmitted
• What is electromagnetic induction?

  When potential difference is induced as a wire or coil moves through a magnetic field
• why cant dc be used in transformers?

  doesn’t create a changing magnetic field
• what happens when you reverse the movement

  you reverse the current
• what is the issue in energy transmission and its solution

  • heat energy is lost due to friction in cables
  • if current decreases so does the energy lost
  • high voltages = lower current so lover energy loss
• what is a step up and step down

  step up - more secondary turns - higher voltage so lower current and energy loss - at power stations

  step down - less secondary turns - lower voltage so higher current and energy loss - at homes - usable level
• what factors affect an induced potential difference and how

  • speed - increases voltage
  • strength of field - stronger voltage
  • number of coils - more turns - higher voltage
  • length of the conductor - longer wire higher voltage
• how do transformers work

  ac in primary creates a changing magnetic field and passes through the iron core to the secondary coil