Q50: A rechargeable battery of mass 15.0 g deliv- ers an average current of 18.0 mA to a portable DVD player at 1.60 V for 2.40 h before the battery must be recharged. The recharger maintains a potential dif- ference of 2.30 V across the battery and delivers a charging current of 13.5 mA for 4.20 h.
(a) What is the efficiency of the battery as an energy storage device?
(b) How much internal energy is produced in the bat- tery during one charge–discharge cycle?
(c) If the battery is surrounded by ideal thermal insulation and has an effective specific heat of 975 J/kg ? °C, by how much will its temperature increase during the cycle?