A source of emf has internal resistance r. (a) What is the terminal voltage when the

Question:

A source of emf ℰ has internal resistance r.
(a) What is the terminal voltage when the source supplies a current I?
(b) The net power supplied is the terminal voltage times the current. Starting with P = IΔV, derive Eq. (18-22) for the net power supplied by the source. Interpret each of the two terms.
(c) Suppose that a battery of emf ℰ and internal resistance r is being recharged: another emf sends a current I through the battery in the reverse direction (from positive terminal to negative). At what rate is electric energy converted to chemical energy in the recharging battery?
(d) What is the power supplied by the recharging circuit to the battery?