Paper 2- Physics

• What is the main purpose of transformers?

  To change the potential difference of electricity
• What are transformers made of?

  Two coils of wire wound onto an iron core
• What is the effect that allows voltage induction in transformers?

  Electromagnetic induction
• What does potential difference (p.d.) measure?

  Energy transferred by each coulomb of charge
• How is electrical power calculated?

  Power = current x potential difference
• What does the equation P = I x V represent?

  Electrical power in terms of current and voltage
• What does the symbol P represent in the equation P = I x V?

  Electrical power
• What does the symbol I represent in the equation P = I x V?

  Current
• What does the symbol V represent in the equation P = I x V?

  Potential difference
• What must be true about the power in a transformer?

  Power in primary equals power in secondary
• What happens if a transformer is 100% efficient?

  Power in secondary equals power in primary
• How can the power relationship in a transformer be expressed mathematically?

  VP x IP = VS x IS
• What is the role of the secondary coil in an electric toothbrush?

  It receives power from the primary coil
• Why is it safe to use an electric toothbrush in a bathroom?

  There is no electrical contact with the charger
• How do you calculate the current drawn from the mains supply for six 50W bulbs using a transformer?

  Use the equation VP x IP = VS x IS
• What is a step-up transformer used for?

  To increase the potential difference of electricity
• What happens to the current when a step-up transformer increases voltage?

  The current decreases at the same time