Direct Current Motors

Motors are used in many equipment, such as fan, blender, pump, etc. How motors work?

Motor is the equipment which convent from electricity to rotation. Before discuss about motor, let us review relation between current, magnetic field and force. See figure 1, Force can be generated by current and magnetic field. If current flow at a wire and it is in the magnetic field, then they are generated some force to the wire. We can see the direction of magnetic field is from North (N) to south (S). By right hand rules, direction of current is showed by I, direction of magnetic field is showed by B, and force is showed by F. Then they are generated force at wire to down direction. We can determine their direction by right hand rule. 

Figure 1. (a)Force, current, and magnetic field; (b) Right hand rule of direction; (c) simple construction DC motor

Now, let us consider the construction of simple direct current motor. The current flows from positive along the wire to negative, the magnetic field direction is from North (N) to South (S). Based on the right hand rules, loop will make rotation like the arrow direction (clock wise).

Brushes are static, but commutators  move (make rotation movements). Commutators will connect to the different pole of electricity (battery) alternately . Then, when the current flows, there will be a force to down direction at the right part of loop and force to up direction at the left part of loop. The construction of simple DC motor make a rotation at one direction (clock wise or counter clock wise) depend on the current flows.

Source of figure: Halliday, Resnick, Walker: Fundamentals of Physics; 
Douglas Giancoly: PHYSICS PRINCIPLES WITH APPLICATIONS