arXiv:0910.5279v1 [physics.ed-ph] 28 Oct 2009 The mystery of lost energy in ideal capacitors A. P. James 1 1 Queensland Micro-nanotechnology Center, Griﬃth University Nathan, QLD 4111, Australia E-mail: a.james@griﬃth.edu.au Abstract The classical two-capacitor problem shows a mysterious lose of en- ergy even under lossless conditions and questions the basic under- standing of energy relation in a capacitor. Here, we present a solution to the classical two-capacitor problem. We ﬁnd that by reinterpreting the energy calculations we achieve no lose of energy thereby obeying the conservation of energy law. The introductory books in electronic circuits and physics [1, 2, 3, 4], of- ten put forward an energy paradox on idealised capacitor switching. This paradox [5] is described in Fig. 1a, where energy before and after the switch become closed does not seem to be same. The main issue here is the mys- terious loss of 50% energy, despite all the components being ideal (i.e. ideal capacitor, ideal wires, and ideal switches). Further, in Fig. 1a, the total charge, total voltage, and total power in the circuit is conserved, so having energy reduced by half questions the primary idea of conservation principle. For the past several decades, as this paradox had no explanation or solution under “idealistic” conditions, much focus has been on rationalising the lose 1