Low core loss and high permeability are the characteristics of the sheet steel material used in transformer cores. This choice, option C, is the correct answer.

Explanation:

Core loss refers to the energy lost in the form of heat when an alternating magnetic field is applied to a core material. It is an important consideration in transformer design because excessive core loss can result in reduced efficiency and increased operating temperatures. On the other hand, permeability is a measure of how easily a material can be magnetized or how well it can conduct magnetic flux.

The sheet steel material used in transformer cores is specifically chosen for its low core loss and high permeability properties due to the following reasons:

1. Low Core Loss:
Sheet steel materials used in transformer cores are designed to have low core loss characteristics. This means that they have a low hysteresis loss and eddy current loss when subjected to varying magnetic fields. Low hysteresis loss is achieved by using steel with low coercivity, which means it requires less energy to magnetize and demagnetize the material. Low eddy current loss is achieved by using materials with high resistivity or by laminating the steel sheets to minimize the flow of eddy currents.

2. High Permeability:
High permeability is desired in transformer cores as it allows for efficient magnetic flux conduction. A material with high permeability can easily magnetize and demagnetize, resulting in a more effective transfer of energy. Sheet steel materials for transformer cores are carefully processed to enhance their magnetic properties, such as grain orientation and controlled annealing, to achieve high permeability.

By selecting sheet steel materials with low core loss and high permeability, transformer designers can minimize energy losses and improve the efficiency of the transformer. This allows for the efficient transfer of electrical energy from one circuit to another with minimal losses and ensures that the transformer operates within acceptable temperature limits.

In conclusion, the sheet steel material used in transformer cores has low core loss and high permeability properties to ensure efficient energy transfer and minimize losses.