Define the term "back EMF" in the context of motors.

Back EMF, or back electromotive force, refers to the voltage that is generated in opposition to the applied voltage when a motor is operating. When a motor spins, it induces a voltage in the opposite direction to the voltage supplied by the power source. This phenomenon occurs due to the motor's rotation in a magnetic field, which causes electromagnetic induction according to Faraday's law.

This opposing voltage is crucial for the operation of the motor because it regulates the amount of current flowing through the windings as the motor speed increases. When the motor is at rest or running at low speeds, back EMF is minimal. However, as speed increases, back EMF rises, reducing the current flow through the motor. This relationship helps in preventing excessive current draw, thus protecting the motor and the power supply from potential damage. Understanding back EMF is essential for comprehending motor control and performance.