The working principle of DC motor (Direct Current) is basically the same as the working principle of AC motor (Alternate Current), the difference in voltage sources where this motor will spin if given direct current.
DC motor can rotate clockwise and counter-clockwise depending on the voltage of the source is given. If the positive pole of the voltage source is connected to the positive terminal of the DC motor and the negative pole of the voltage source is connected to the negative terminal of DC motor, then the motor will rotate clockwise and otherwise if the poles of the voltage source is reversed, the motor will rotate counter-clockwise.
Just as AC motors, DC motors have two main parts, namely the stator magnetic part does not rotate and the rotator coils in the middle and that can rotate if electrified. The working principle of a DC motor is based on the electromagnetic force caused by the electric current that goes to the coil on the rotator. Magnetic induction occurs in the rotator will repel each other with a permanent magnet on the stator so consequently the motor will spin.
DC motors generally have low power and are used in electronic equipment with a small current. For general purposes, this DC motor can be easily found at electronic stores and electrical shops. DC motors are very beneficial to human life because many devices use power DC motors such as toys, robots, CD ROM, hard drive, printer, etc.
DC motors are often used not only on household devices but also many industries that utilize the working principle of a DC motor to run a small industrial engines that require a motor with low power. Though DC motors can rotate with the DC power supply and can rotate back and forth (in a clockwise direction and the opposite direction clockwise) by reversing the polarity of the voltage source, but any DC motor has the characteristics of different plants as needed, for example a limit voltage source.
Example, 12 Volt DC motor means the motor can work optimally if given a 12 Volt DC source voltage. If the applied voltage is less than 12 volts, then the motor will rotate slowly even not spinning at all. Likewise, if the motor is given the supply voltage exceeds 12 Volts, then the motor will spin faster, but can cause damage. Therefore, you should read the characteristics of a DC motor which is located on the label before use.