Explanation:

An auto transformer is a type of transformer in which the primary and secondary windings are connected together and share a common winding. This configuration allows for a part of the energy transfer to occur through the conduction process.

Conduction Process:
In the conduction process, energy transfer occurs through direct contact between two objects. In the case of an auto transformer, the primary and secondary windings are in direct contact with each other through the common winding. This allows for the transfer of energy from the primary winding to the secondary winding through the process of conduction.

- The primary winding is connected to a power source, and when current flows through it, a magnetic field is generated.
- This magnetic field induces a voltage in the secondary winding, which is connected to the load.
- The voltage induced in the secondary winding is directly proportional to the turns ratio between the primary and secondary windings.
- Since the primary and secondary windings share a common winding, the energy transfer from the primary to the secondary winding occurs through direct contact between the windings.
- This direct contact allows for efficient transfer of energy, as there is minimal loss due to impedance or resistance between the windings.

Other Processes:
While conduction is the main process of energy transfer in an auto transformer, other processes such as convection, induction, and radiation may also play a minor role in the overall energy transfer.

- Convection: Convection is the process of energy transfer through the movement of fluids or gases. In an auto transformer, there may be some heat dissipation due to the flow of coolant or air around the transformer. This heat dissipation occurs through the convection process.
- Induction: Induction is the process of energy transfer through electromagnetic fields. In an auto transformer, there may be some energy transfer through induction due to the close proximity of the primary and secondary windings. However, the conduction process is the dominant mode of energy transfer in an auto transformer.
- Radiation: Radiation is the process of energy transfer through electromagnetic waves. In an auto transformer, there may be some energy transfer through radiation, but it is typically minimal compared to the conduction process.

In conclusion, the correct answer to the question is option 'B' - conduction process. The primary and secondary windings of an auto transformer share a common winding, allowing for efficient energy transfer through direct contact between the windings.