Each of two identical electricity storage batteries can exchange energy with the surroundings exclusively through its terminals, that is, each battery is perfectly isolated except for connections that can be made to the electrical terminals. Each battery is initially charged with 100 MJ of electrical energy.
The terminals of battery A are connected to a resistance heating element. As a result, 75 MJ of energy is transferred out of the battery. then battery A is let untouched for a year. Battery B is let completely untouched, also for a year. At the end of the year, both batteries are found completely discharged.
(a) What is the final energy of each battery?
(b) A perfect motor is defined as a device that can transfer to a weight 100% of the electrical energy it receives. How much energy can be transferred to a weight upon connecting a perfect motor to the terminals of either battery in the initial state? How much in the intermediate state of battery A just after it supplied energy to the heater? How much in the final state of either battery?
