Research to the motors is based on the following five scientific laws. In order to have a preliminary acquaintance to
motor principles, we need to known these laws first.
(1)  Law of electromagnetic induction (Faraday 1831) 
Conductors (of finite dimensions) moving through a uniform magnetic field will have currents induced within
them. The direction of the current is judged by right hand rule
and follows the equation:
E=B*L*V
E: Electromotive force (Unit: V)
B: Magnetic flux density of magnetic field (1 Tesla=104 Gauss)
L: Effective length of conductor (Unit: m)
V: Velocity of the conductor (Unit: m/s)
See figure 1 to the right, if we connect a lead wire to the conductor,
induced current will be generated.
(2)  Biot-Savart Law
Conductors with current within them will generate electromagnetic force in amagnetic field. The direction is
judged by left hand rule, (see figure 2) and follows the equation:
F=B*I*L
F: Electromagnetic force (Unit: N)
I: Current in the inductor (Unit: A)
B: Magnetic flux density of the magnetic field (Unit: Tesla)
L: Effective length of the conductor (Unit: m)
Left hand rule is also called as motor rule.
Right hand rule isalso called as generator rule.
(3)  Kirchhoff's circuit laws (See figure 3)
KCL ΣI=0: At any node (junction) in an electrical circuit, 
the sum of currents flowing into that node is equal to 
the sum of currents flowing out of that node
KVL ΣU=0: The directed sum of the electrical potential 
differences (voltage) around any closed network is zero.
(4)  Law of conservation of energy 
The total amount of energy in an isolated system remains constant over time. 
(5)   Ampère's circuital law
In short, conductors with current within them generate magnetic field 
around them. The direction of the magnetic filed is judged by right 
hand thrumb rule and follows the equation. See figure 4
∮H×dL=∑I=IA+IB+IC+…
H: magnetic field intensity (Unit: A/M)
L: Length of conductor (Unit: M)
I: Current (Unit: A)