The two coupling models most frequently used in the power-lightning literature for the calculation of lightning-induced overvoltages, namely the model by Chowdhuri and Gross (1967) and the model by Agrawal, Price and Gurbaxani (1980), are compared and discussed. It is shown that the Chowdhuri-Gross model is incomplete: the source term due to the contribution of the magnetic induction is missing. The authors investigate how much the lack of the source term affects the accuracy of the calculated overvoltages. Experimental tests of the two models using a short line illuminated by a NEMP simulator support the theoretical conclusion