Hi Aspirant!

Current is the flow of electrons from an electrically abundant source to an electrically deficit destination, means a flow of electrons from higher to lower concentration. It is denoted by 'I' and its unit is Ampere , denoted by 'A'.

I = q/t ; where q is in coulombs and t is in seconds.

However, some books mention current as 'i' (as you mentioned) there is nothing wrong with that but as per the definition, I would suggest you to use 'I' instead of 'i'.

Thankyou!