Water turbines are turbo machines utilizing water power. The Francis turbine is part of the reaction turbines which convert the pressure energy of the water into kinetic energy in the control device and in the impeller. The water is fed in the control device by means of a spiral tube. The flowing water is accelerated in the control device by the adjustable guide vanes and directed onto the vanes of the impeller. The redirection and further acceleration of the water in the impeller generates an impulse which is transmitted to the Francis wheel. This apparatus is the model of a Francis turbine demonstrating the function of a reaction turbine. The apparatus consists of the Francis wheel, the control device with adjustable guide vanes, a band brake for loading the turbine and housing with a transparent front panel. The transparent c