In order to heat a liquid an electric heating coil is connected is to a cell of emf `E = 12 V` and internal resistance `r = 1 Omega`. There are three options for selecting the resistance `(R)` of the heating coil. `R` can be chosen as `1 Omega, 2 Omega or 4 Omega`. The cell has a rating of `2000 mAh` (milli Ampere hour) and it is to be used to heat the liquid till it expires. [The cell maintains constant emf till it lasts]
(a) Which value of R will you chose so that maximum heat `(H_0)` is transferred to the liquid before the cell expires? Calculate `H_(0)`.
(b) Which value of `R` will chose so that heat is transferred to the liquid at fastest possible rate? What percentage of `H_(0)` (as obtained in (a)) is transferred to the liquid in this case by the time the cell expires ?

Answer

(a) `4 Omega,69.12 kJ`
(b) `1 Omega,62.5 %`