This paper focuses on an analytical approach to study a MHD generator supplied with an oscillating pressure . The oscillating pressure moves inside the device a liquid metal which represents the operating fluid, which is immersed in a DC magnetic field generated by a permanent magnet. The interaction between the moving liquid metal and the applied magnetic field induces an alternate electrical current in the liquid. Such current performs as the primary of a transformer, the secondary being represented by an external winding connected to the electrical load. In this paper the analytical model is developed, and some preliminary results are reported.