HSC Physics Transformers

Most HSC students can apply the transformer equation, but often the Physics principles are misunderstood. A tutorial sheet on transformers is given below.

  1. What is the role of a transformer in the transmission of electricity?
  2. Define one volt.
  3. Define the term emf.
  4. Is voltage is the same as emf?
  5. What is the role of the iron core in a transformer?
  6. What is meant by a soft iron core? Why is the soft iron core laminated?
  7. Can a transformer operate using DC? Sketch a graph showing the primary and secondary voltage (on different axes) when the DC voltage applied to the primary coil is switched on and then after a short time switched off.
  8. A common examination response is that "the induced emf in a coil equals the rate of change of the magnetic flux through the coil". Why is this incorrect?
  9. When AC enters the primary coil of a transformer in which coil is an emf induced? Primary, secondary or both?
  10. Assuming that the primary coil has low resistance, is the voltage applied to the primary coil equal to the counter emf induced in the primary coil? Is a counter emf induced in the secondary coil?
  11. Explain how an emf is induced in the secondary coil.
  12. The transformer equation uses the symbols Vp and Vs. Since transformers use AC, in which the current varies with time, what do these symbols represent?