DC motor

A DC motor is the simplest, cheapest electric motor: connect it to a battery and the shaft spins. "DC" means direct current — the steady, one-direction electricity a battery gives, as opposed to the back-and-forth current from a wall socket. These are the little motors humming inside toys, drills, and many small robots. Reverse the battery's two wires and the motor spins the other way; that simplicity is exactly why beginners reach for them first.

Inside, it works by a trick of magnetism. A coil of wire sits between magnets, and when current flows through the coil it becomes a temporary electromagnet, pushed and pulled by the fixed magnets so it turns. But to keep turning the same way, the current in the coil must flip direction at just the right moment in every rotation. A clever rotating switch called the commutator does this automatically, with little carbon blocks called brushes sliding against it to feed in the current. That is why this everyday type is more precisely called a brushed DC motor.

Its behavior follows a simple rule called the torque-speed curve. With no load, it spins fast but gives almost no twisting force; pile on a heavy load and it slows down while pushing harder, until at full load it stalls — stops turning while drawing the most current and producing its peak twist. Feed it more voltage and it spins faster; this voltage-driven simplicity makes it easy and forgiving to drive. The trade-off is the brushes: they rub, wear out, and spark, so brushed motors are noisier and shorter-lived than their brushless cousins.