Question

Human brain and the nervous system essentially consists of electrical circuitry. An average adult consumes 2800 Kcal. of energy daily in the form of food. Estimate the average power consumption of brain (in watts) if the organ uses one fifth of the total consumed energy. There is no gross change in the cerebral activity during sleep that lasts for an average duration of 7 hours per day.

Answer 1

Convert kilocalories to joules (you may multiply calories by 4180):

2800 kcal is 11720240 Joules.

Brain consumes 1/5 of that:

$$E_B=11720240/5=2344048\text{ J}.$$

Power in Watts is energy in Joules per time in seconds:

$$P=\frac{E_B}{t}=\frac{2344048}{24\cdot3600}=27\text{ W}.$$