The power supply used in an electric vehicle contains 990 rechargeable cells each of electromotive force (e.m.f.) 1.2V. The cells are contained in packs in which all the cells are in series with each other. The e.m.f. of each pack is 54 V. (a) Calculate the number of packs in the power supply. number of packs = (b) When in use, each pack supplies a current of 3.5 A. (i) Calculate the rate at which each cell is transferring chemical energy to electrical energy. [2] rate of energy transfer= [2] (ii) The packs are connected in parallel to supply a large current to drive the electric vehicle. Explain why it is necessary to use thick wires to carry this current.
