Transformer calculations

• 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 \( V_P = 45 \) volts and \( N_P = 18 \) turns?

  45 volts
• How do you calculate the output potential difference \( V_S \) using the transformer equation?

  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 and \( V_P = 45 \) volts with \( V_S = 135 \) volts?


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

  1. \( \frac{V_P}{V_S} = \frac{N_P}{N_S} \)
  2. \( \frac{I_P}{I_S} = \frac{N_S}{N_P} \)