Question

What is the principle of a transformer? Explain the working process of a step-up transformer by drawing a circuit diagram. Enunciate any two reasons of energy losses in transformer.

Hint:

Step-up transformer: $N_s > N_p$, increases voltage. Step-down transformer: $N_s < N_p$, decreases voltage.

Answer 1

Step 1: Principle.
A transformer works on the principle of mutual induction, i.e., when alternating current flows through the primary coil, it produces a changing magnetic flux, which induces an emf in the secondary coil.
Step 2: Step-up transformer working.
- In a step-up transformer, the number of turns in the secondary coil ($N_s$) is greater than that in the primary coil ($N_p$). - The emf ratio is: \[ \frac{E_s}{E_p} = \frac{N_s}{N_p}. \] - Hence, voltage across secondary increases, while current decreases correspondingly to conserve power.
Step 3: Circuit diagram.
(Insert simple diagram: AC source connected to primary coil; secondary coil connected to load, with $N_s>N_p$).
Step 4: Energy losses in transformer.
Two common reasons: 1. Eddy current loss: Currents induced in the iron core produce heating. Laminating the core reduces this. 2. Hysteresis loss: Repeated magnetization and demagnetization of the iron core consumes energy. Using soft iron with small hysteresis loop minimizes this.
Step 5: Conclusion.
Thus, a transformer is based on mutual induction. In a step-up transformer, voltage is increased by using more turns in the secondary. Energy losses occur due to eddy currents and hysteresis.