Memory Anchor:

• Super Challenge:

  Stretch:

  Challenge:

Key Questions:

1. (Physics only) How does the equation linking the pds and number of turns in the two coils of a transformer link to the to the currents and the power transfer involved. Relate these to the advantages of power transmission at high potential difference.
   • At the end of the power station there is a step up transformer which increases the voltage but decreases the current therefore less Energy is lost by heat. Before the current reaches homes and industry a step down transformer steps up the current and steps down the voltage.
2. (Physics only) What is the basic structure of a transformer?
   • (Physics only) A basic transformer consists of a primary coil and a secondary coil wound on an iron core.
3. (Physics only) Which metal is used for the core in transformers?
   • (Physics only) Iron is used [for a core] as it is easily magnetised.
4. (Physics only) The ratio of the potential differences across the primary and secondary coils of a transformer (Vp and Vs) depends upon the ratio of what?
   • The potential differences across primary and secondary coils of a transformer depend upon the ratio of number of turns on each primary and secondary coil (np and ns)
5. (Physics only) In a step-up transformer which has the greatest potential difference, primary (Vp) or secondary (Vs) coils?
   • In a step-up transformer Vs > Vp (Primary potential difference = Vp; Secondary potential difference = Vs)
6. (Physics only) In a step-down transformer which has the greatest potential difference, primary (Vp) or secondary (Vs) coils?
   • In a step-down transformer Vp > Vs (Primary potential difference = Vp; Secondary potential difference = Vs)
7. (Physics only) What would the relationship be between total power input and output in a transformer if it were 100% efficient?
   • If transformers were 100 % efficient, the electrical power output would BE EQUAL to the electrical power input.
8. (Physics only) Vp x Ip = the ______ _______ (primary coil). power input Vs x Is = the _______ ______ (secondary coil)power output
   • Vp x Ip = the POWER INPUT(primary coil). Vs x Is = the POWER OUTPUT (secondary coil) (Ip = Current through primary coils Is = Current through secondary coils)
9. (Physics only)Explain how the effect of an alternating current induces a current in another transformer.
   • An alternating current in a transformer creates a changing magnetic field. A changing magnetic field also induces a changing voltage in a coil. This is the basis of how a transformer works: The primary coil is connected to an AC supply An alternating current passes through a primary coil wrapped around a soft iron core The changing current produces a changing magnetic field This induces an alternating voltage in the secondary coil This induces an alternating current (AC) in the circuit connected to the secondary coil
10. (Physics only) How does the ratio of the potential differences across the two coils depends on the ratio of the number of turns on each?
    • The ratio of the potential differences across the two coils depends on the ratio of the number of turns on each