Question

Name the device used to transform 12 V a.c. to 200 V a.c. Name the principle on which it works.
A. Step down transformer, magnetic induction
B. Step down transformer, electromagnetic induction
C. Step up transformer, magnetic induction
D. Step up transformer, electromagnetic induction

Answer 1

Hint : A transformer is a device which is used to transfer electrical energy from one circuit to another. Its working is based on the mutual induction of two coils placed in vicinity of each other.

Complete step by step solution :
A transformer is an electrical device which is used to couple one circuit to another. The transformer transforms the electrical energy from one circuit to another.
A transformer is constructed using two coils wound around a laminated steel core. All the components are electrically insulated from one another
The basic working principle of a transformer is electromagnetic induction which involves mutual inductance between the coils of the transformer. In a transformer, we have a primary coil and a secondary coil. An input signal is fed to the primary coil. The change in flux in secondary coil due to flow of current in primary coil induces an e.m.f in secondary coil. The amount of e.m.f produced in the coils depends on the number of windings of the coils.
On the basis of windings, we have two types of transformers:
1. Step-down transformer: The primary coil has more windings than secondary coil. It decreases or steps down the voltage.

2. Step-up transformer: The secondary coil has more windings than primary coil. It increases or steps up the voltage.

Therefore, on the basis of above discussion, we need a step-up transformer to transform 12 V a.c. to 200 V a.c. and it works on the principle of electromagnetic induction.

So, the correct answer is “Option D”.

Note : 1. The electromagnetic induction implies that the working of a transformer involves both electric and magnetic effects of current.
2. We use a laminated steel core in a transformer because it reduces losses due to eddy currents. Eddy currents are currents which are set up in a conductor due to changing magnetic fields around it. They are not useful and lead to loss of energy.