PHYSICS · Multi-part · AP · Physics 2: Algebra-based · Electric Circuits · Electric Circuits
Problem
A storage battery is marked "1200 Wh, 12 V".
Answer the following questions with suitable reasoning.
(i) Explain the physical meaning of the figures 1200 Wh and 12 V written on the battery.
(ii) Starting from the definition of electrical power and electrical energy, show that the time for which a device of constant power P can be run by this battery is given by t=P1200Wh, provided the battery is ideal.
(iii) The battery actually delivers energy with an overall efficiency of only 85 %. Explain qualitatively how this efficiency alters the running time obtained in part (ii).