Question

In transformer, core is made of soft iron to reduce \(\ldots \ldots\) (a) Hysteresis losses (b) Eddy current losses (c) Force opposing current (d) the weight

Short answer

The correct answer is (a) Hysteresis losses. Using soft iron in transformer cores helps reduce hysteresis losses, which improves the energy efficiency of the transformer.

Step-by-step solution

Understanding Hysteresis Losses

Hysteresis loss is the energy loss in a magnetic material due to the reversal of magnetization when the AC current flows through it. In transformers, this loss mainly occurs in the core. Soft iron exhibits a small hysteresis loop, which means lower energy loss during the magnetization reversal process in the core. Therefore, using soft iron in transformer cores can help in the reduction of hysteresis losses.

Understanding Eddy Current Losses

Eddy current loss is caused by the flow of induced currents, called eddy currents, within the transformer core. The fluctuating magnetic field produced by the AC currents generates these eddy currents. Eddy currents result in energy loss through heat produced by resistive heating. Now let's analyze each option to determine which is the correct answer.

Analyzing Options

(a) Hysteresis losses - As discussed earlier, using soft iron can help reduce hysteresis losses. So, this is a potential correct answer. (b) Eddy current losses - Soft iron is a good conductor and has high permeability, but it also has a relatively low resistivity compared to other core materials, which makes it more prone to eddy current losses. So, this option is not correct. (c) Force opposing current - There isn't any direct relation between soft iron used in the core and the reduction of any force opposing current. So, this option is not correct. (d) the weight - The weight of the core depends on the volume and density of the material used. Soft iron is chosen primarily for its magnetic properties and not for its weight reduction properties. So, this option is not correct.

Conclusion

The correct answer is (a) Hysteresis losses. Using soft iron in transformer cores helps reduce hysteresis losses, which improves the energy efficiency of the transformer.