for all those curious about the motor works, i got good explaination on the wikipedia this is the summary:

When a current passes through the coil wound around a soft iron core, the side of the positive pole is acted upon by an upwards force, while the other side is acted upon by a downward force. According to Fleming's left hand rule, the forces cause a turning effect on the coil, making it rotate. To make the motor rotate in a constant direction, "direct current" commutators make the current reverse in direction every half a cycle thus causing the motor to rotate in the same direction.

The problem facing the motor shown above, is when the plane of the coil is parallel to the magnetic field; i.e. the torque is ZERO-when the rotor poles or displaced 90 degree from the stator poles. The motor would not be able to start in this position, but the coil can continue to rotate by inertia.

There is a secondary problem with this simple two-pole design; at the zero-torque position, both commutator brushes are touching across both commutator plates, resulting in a short-circuit that uselessly consumes power without producing any motion. In a low-current battery-powered demonstration this short-circuiting is generally not considered harmful, but if a two-pole motor were designed to do actual work with several hundred watts of power output, this shorting could result in severe commutator overheating, brush damage, and potential welding of the metallic brushes to the commutator.

Unlike the demonstration motor, above, DC motors are commonly designed with more than two poles, are able to start at any position, and do not have any position where current can flow without producing electromotive power.

If the shaft of a DC motor is turned by an external force, the motor will act like a generator and produce an Electromotive force (EMF). During normal operation, the spinning of the motor produces a voltage, known as the counter-EMF (CEMF) or back EMF, because it opposes the applied voltage on the motor. This is the same EMF that is produced when the motor is used as a generator (for example when an electrical load (resistance) is placed across the terminals of the motor and the motor shaft is driven with an external torque). Therefore, the voltage drop across a motor consists of the voltage drop, due to this CEMF, and the parasitic voltage drop resulting from the internal resistance of the armature's windings.As an unloaded DC motor spins, it generates a backwards-flowing electromotive force that resists the current being applied to the motor. The current flow through the motor drops as the rotational speed increases, and a free-spinning motor has very little current flow. It is only when a load is applied to the motor that slows the rotor that the current draw through the motor increases.Apparantly, if the motor had been helped on to run at 261.5 revolutions per minute, the current would have been reduced to zero. In the last result obtained, the current of 5.1 amperes was absorbed in driving the armature against its own friction at the speed of 195 revolutions per minute."
(1917) Hawkins Electrical Guide. Theo. Audel & Co., 359.