Turbines can be divided into four general types depending on the fluid used: water, steam, gas and wind. Although the same principles apply to all turbines, their specific design varies widely and is worthy of being described separately. Turbine, any device that converts energy in a fluid into mechanical energy. Switching is typically accomplished by passing fluid through a fixed passage or vane system that alternates with a passage of finned vanes connected to the rotor. By arranging the flow so that a tangential force or torque is applied to the rotor blades, the rotor rotates and the work is extracted.