What does the term "back EMF" refer to in electric motors?

The term "back EMF" refers specifically to the reverse voltage produced as the motor turns. In electric motors, when current flows through the motor windings, it generates a magnetic field that interacts with the rotor. As the rotor spins, it cuts through the magnetic field, which induces a voltage in the opposite direction of the applied voltage. This induced voltage is known as back EMF.

Back EMF plays a critical role in the operation of electric motors. It acts to limit the current flowing through the motor as its speed increases. When the motor is at a standstill or stalled, the back EMF is zero, leading to maximum current draw, which can potentially cause overheating or damage. As the motor accelerates, back EMF increases and opposes the power supply voltage, thus reducing the overall current and helping to regulate the operation of the motor under load.

Understanding back EMF is essential for grasping how motors operate efficiently and how factors such as load and speed affect current draw and performance.