Transformers MCQ Questions & Answers | Electrical Engineering

The purpose of providing an iron core in a transformer is to decrease the reluctance of the magnetic path.

The iron core is used to improve the efficiency of the transformer by providing a low reluctance path for the magnetic flux. This allows the transformer to transfer electrical energy more effectively between its windings.

Key Points:
Iron Core: Reduces the reluctance (magnetic resistance) of the magnetic path, enhancing the transformer's efficiency.
Reluctance: The resistance to the flow of magnetic flux. By decreasing reluctance, the core helps in better flux linkage between the primary and secondary windings.

Copper loss in a transformer is due to the current flowing through the windings' resistance.
It's also known as I²R loss (where I is current and R is resistance).
Importantly, copper loss varies with the square of the load current.
Let's denote the full-load current as I_FL.
The copper loss at full load (P_{cu_FL}) is proportional to (I_FL)².
P_{cu_FL} = k * (I_FL)² = 1600 W (where k is a constant related to the winding resistance).
At half-load, the current is I_FL / 2.
The copper loss at half-load (P_{cu_HL}) is proportional to (I_FL / 2)².
P_{cu_HL} = k * (I_FL / 2)² = k * (I_FL)² / 4.
Since k * (I_FL)² = 1600 W, then P_{cu_HL} = 1600 W / 4 = 400 W.
Therefore, the copper loss at half-load is 400 W.

Transformers are static electrical devices, meaning they have no moving parts.
Because of this, there are no mechanical losses such as friction or windage losses, which occur only in rotating machines like motors or generators.

Core losses (which include hysteresis and eddy current losses) occur whenever the transformer core is energized — that is, even under no-load conditions. These losses depend on the supply voltage and frequency, not on the load.

Copper losses occur only when the transformer carries load current and vary with the square of the load current.

Since a transformer has no moving parts, the friction loss is zero at all times — even at full load.

Hence, the correct answer is Friction loss.