I'm reading a textbook with a section on DC motors that claims the following:
"A seemingly obvious approach to control the speed of a dc motor would be simply to limit the current flow by using a potentiometer, as shown in the circuit to the left in the figure (the figure is a motor and potentiometer in series). According to Ohm’s law, as the resistance of the pot increases, the current decreases, and the motor will slow down. However, using a pot to control the current flow is inefficient. As the pot’s resistance increases, the amount of current energy that must be converted into heat increases."
But according to Ohm's law, shouldn't the power through the resistor (and thus the heat generated) increase as the resistance decreases? What am I missing?
"A seemingly obvious approach to control the speed of a dc motor would be simply to limit the current flow by using a potentiometer, as shown in the circuit to the left in the figure (the figure is a motor and potentiometer in series). According to Ohm’s law, as the resistance of the pot increases, the current decreases, and the motor will slow down. However, using a pot to control the current flow is inefficient. As the pot’s resistance increases, the amount of current energy that must be converted into heat increases."
But according to Ohm's law, shouldn't the power through the resistor (and thus the heat generated) increase as the resistance decreases? What am I missing?