 This paper presents an analytical study of the air-gap magnetic field of a surface permanent magnet, SPM, linear machine under no load. Using the method of images, the complex expression of the magnetic field of a conductor, inside the air-gap between two smooth iron surfaces, can be retrieved. Integrating this expression, the formulation of the magnetic field of a current sheet and thus the one of a SPM, using two vertical current sheets, can be obtained. At last, the no load magnetic field expression, for a generic time instant, of a slotless machine can be retrieved. The novelty of the proposed approach is the availability, due to a different calculation approach, of a unique closed form formulation for the slotless machine air-gap field, a quantity that, in literature, is usually present in Fourier series formulation. Additionally, as a means to calculate integral quantities and show the goodness of the method, a complex slotting function has been introduced to account for the slotted geometry. Finally, starting from Lorenz's force formulation, the expression of the Maxwell tensor in complex form has been retrieved and the contribution of forces, integral of the complex stress tensor quantity, will be This article was authored by Antonino de Gerlando and Claudio Ricca. We are article.tv, links in the description below.