Question

Draw a labelled diagram of a device you would use to transform 200 V a.c. to 15 V a.c. Name the device and explain how it works. Give its two uses.

Answer 1

In the given question, a step down transformer will be used to transform 200 V a.c. to 15 V a.c.
The transformer works in the principle of Electromagnetic induction which states that rate of change of flux linkage with respect to time is directly proportional to the induced EMF in a conductor or coil.
Say we have one winding which is supplied by an alternating electrical source. The alternating current through the winding produces a continually changing flux or alternating flux that surrounds the winding. If any other winding is brought nearer to the previous one, obviously some portion of this flux will link with the second. As this flux is continually changing in its amplitude and direction, there must be a change in flux linkage in the second winding or coil. According to Faraday's law of electromagnetic induction, there must be an EMF induced in the second. If the circuit of the later winding is closed, there must be an current flowing through it. This is the simplest form of electrical power transformer and this is the most basic of working principle of transformer.
On a step-down transformer there are more turns on the primary coil than the secondary coil. The induced voltage across the primary coil is greater than the applied voltage across the secondary coil or in other words the voltage has been stepped-down".
Uses of step-down transformer:

• Step down transformers are designed to reduce electrical voltage. Their primary voltage is greater than their secondary voltage. For instance, a step down transformer is needed to use a 110v product in a country with a 220v supply.
• Step down transformers convert electrical voltage from one level or phase configuration usually down to a lower level. They can include features for electrical isolation, power distribution, and control and instrumentation applications.