Transformers

• What is the primary function of transformers in the national grid?

  To increase or decrease voltage
• Why is electricity generated at huge power stations spread out across the UK?

  To ensure widespread electricity availability
• What voltage do step-up transformers increase electricity to?

  Around 400,000 volts
• What is the purpose of increasing voltage in the national grid?

  To minimize energy losses during transmission
• What voltage do step-down transformers decrease electricity to?

  Around 230 volts
• Why is it safe to use 230 volts in houses?

  It is a lower, safer voltage for appliances
• What are the main components of a transformer?

  • Primary coil
  • Secondary coil
  • Iron core
• What happens when an alternating potential difference is applied to the primary coil?

  A current flows and generates a magnetic field
• How does the magnetic field in the primary coil affect the iron core?

  It induces an alternating magnetic field in the core
• What does the iron core do in a transformer?

  It connects the primary and secondary coils
• What is induced across the secondary coil due to the iron core's magnetic field?

  A potential difference
• Why can't electricity pass directly from the primary to the secondary coil?

  Wires are insulated in plastic
• If a step-up transformer has twice as many turns in the secondary coil, what happens to the voltage?

  It gets doubled
• What is the difference between a step-up and a step-down transformer?

  Step-up increases voltage; step-down decreases it
• What is the output voltage of a step-up transformer with a 10 volt input?

  20 volts
• How does the number of turns in the coils affect voltage in transformers?

  More turns increase voltage; fewer turns decrease it
• What are the steps involved in how a transformer works?

  1. Alternating potential difference applied to primary coil
  2. Current flows, generating a magnetic field
  3. Alternating magnetic field induces magnetic field in iron core
  4. Iron core induces potential difference across secondary coil
  5. Current flows in the secondary coil
• What is the purpose of transformers?

  To change the potential difference of electricity supply
• How do step-up transformers increase potential difference?

  They have more turns on the secondary coil
• How do step-down transformers decrease potential difference?

  They have less turns on the secondary coil
• What do the variables in the transformer equations represent?

  • \( V \): Potential difference
  • \( N \): Number of turns on the coil
  • \( I \): Current
  • \( P \): Primary coil
  • \( S \): Secondary coil
• If a transformer has 18 turns on the primary coil and 54 turns on the secondary coil, what is the ratio of turns?

  The ratio is 1:3
• What is the input potential difference if the transformer has 18 turns on the primary coil and 54 turns on the secondary coil?

  45 volts
• How do you calculate the output potential difference \( V_s \) in a transformer?

  Use \( \frac{V_p}{V_s} = \frac{N_p}{N_s} \)
• What is the output potential difference \( V_s \) if \( V_p = 45 \) volts, \( N_p = 18 \), and \( N_s = 54 \)?

  135 volts
• If the input current \( I_p \) is 12 amps, how do you find the output current \( I_s \)?

  Use \( V_p \times I_p = V_s \times I_s \)
• What is the output current \( I_s \) if \( I_p = 12 \) amps, \( V_p = 45 \) volts, and \( V_s = 135 \) volts?

  4 amps
• What are the two main equations used for transformers?


  1. \( \frac{V_p}{V_s} = \frac{N_p}{N_s} \)
  2. \( V_p \times I_p = V_s \times I_s \)