Method of speed regulation by connecting resistors in series in armature circuit

Method of speed regulation by connecting resistors in series in armature circuit

The speed regulation circuit of a DC motor achieves speed regulation by connecting a variable resistor in series with
    the armature loop , as shown in the figure. This approach increases losses in the series resistor , making the motor less efficient. If the load changes slightly, the motor speed will change greatly, which is unfavorable for loads that require constant speed.