Abstarct: The need to find new solutions for modern technologies creates new materials with unique properties. Ferrofluid materials are used as a group of materials with unique and impressive properties in various fields. In recent decades, the development of technology and applications of ferrofluid materials and magnetic fluids has led to positive developments in various industries, and it is predicted that in the future these materials and technologies related to them will greatly contribute to increasing the productivity and sustainability of energy sources. Since the development of electric machines, choosing the right material for the production of the core has a significant effect on its performance. By choosing the right core, the ability to optimize the dimensions and weight of the transformer is provided. In this thesis, the design of a transformer with a ferrofluid core and the effect of concentration on the output voltage have been investigated, as well as the calculation of the equivalent circuit.Then, the application of ferrofluid in electric machines has been investigated by making a new rotor, baxsed on the use of ferrofluid in an axial flux machine. In the following, this machine is modeled with the help of reluctance machine model. The results show that the performance of the ferrofluid machine is very similar to the hysteresis machines and maybe these machines can be used in applications similar to the hysteresis machines. Also, the results of practical testing, parameter calculation, Simulixnk MATLAB modeling and simulation confirm the ability and potential of using ferrofluid in electric machines and show the emergence of new applications of this type of electric machines.