Which body process converts physical energy to electrical energy?

The correct answer is transduction.

Explanation:

Transduction refers to the biological phenomenon in which any external physical stimuli is attained and transmitted from one section of the body to another. At this time, the physical energy, that is, the stimuli get transformed into electrochemical stimuli.  

In the nervous system, transduction generally signifies the stimulus-alerting events in which a physical stimulus is transformed into an action potential, which is conducted along the axons towards the CNS for integration. A receptor cell transforms the energy of a stimulus into an electrical signal.