Topic 13: Electromagnetic induction

• What is the purpose of a transformer?

  to change the voltage of an alternating current (AC)
• What factors affect induced potential difference (voltage)?

  • The speed of movement – Faster movement of the wire or magnet increases the induced voltage.
  • The strength of the magnetic field – A stronger magnetic field results in a greater induced voltage.
  • The number of coils in a wire – More coils in a wire (such as in a solenoid) increases the induced voltage.
  • The angle of movement – The most voltage is induced when the conductor moves perpendicular to the magnetic field lines.
• Describe how a step-up/step-down transformer works

  • AC flows through the primary coil, inducing an alternating magnetic field (just a field that changes direction quick and often)
  • The iron core directs this changing field to the secondary coil.
  • This induces a voltage in the secondary coil.
  • The voltage depends on the number of turns in each coil:
  • More turns in secondary → Higher voltage (Step-Up Transformer)
  • Fewer turns in secondary → Lower voltage (Step-Down Transformer)
• Why is electricity transported using the national grid and transformers? Answer by explaining how it works.

  1. power stations use a step up transformer to increase the voltage while keeping the same power, which reduces the energy lost as this reduces the current (power = voltage x current) - high current = high resistance = lots of heat produced
  2. a step down transformer is then used to reduce the voltage to 240v so its at a safer level to be transported and used in homes
• What is the transformer (with 100% efficiency power) equation?

  pd/voltage across primary coil x current in primary coil = pd/voltage across secondary coil x current in secondary coil