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Rafadha ni chombo chenye umbo la panka kinachozunguka na kusogeza mota ya umeme au ndege hewani na meli majini.
Rafadha ya umeme ni tofauti na rafadha ya mwendo (ndege na meli) kwa sababu inazungushwa kwa kawi ya mbinu ili kutengeneza kawi ya umeme ilhali rafadha ya mwendo huzungushwa kwa kawi ya umeme ili kutengeneza kawi ya mbinu.
Baina ya rafadha za mwendo, ile ya ndege hufanya kazi kwa mkondo tofauti na ile ya meli. Rafadha inapozunguka, mikono yake hutengeneza mkondo katika maji(meli) au hewa(ndege). Mkondo huu unasababisha mwinuko wa kani-eneo yaani, tofauti katika kani ya maji/hewa kwa jumla na kani-eneo ndani ya mkondo. Umbo la mikono ya rafadha na mweleko wa mzunguko husababisha kani-eneo kubwa au dogo na hivyo rafadha inaweza kuvuta au kusukuma chombo chake. Rafadha ya meli kwa kawaida imetengenezwa ili kusukuma chombo ilhali rafadha ya ndege kwa kawaida imetengenzwa ili kuvuta chombo.
[A propeller/turbine is a craft with the shape of a fan that rotates and moves an electric motor or an airplane in the air and ship in the water.
A turbine is different from a propeller (airplane and ship) because it is rotated by mechanical energy so as to produce electrical energy while the propeller is rotated by electrical energy so as to produce mechanical energy.
Among propellers, that of the airplane works in a different way to that of the ship. When a propeller rotates, it’s arms create a current in the water(ship) or air(airplane). This current causes a lifting force-field as in, a difference in the general force of the water/air and the force-field within the current. The shape of the arms of a propeller and its direction of rotation causes a force-field that is either big or small so that the propeller can either pull or push its craft. The propeller of a ship is usually made to push the craft while the propeller of an airplane is usually made to pull the craft.]
