What happens to the starting torque when the potential difference is reduced during motor start-up?

When the potential difference supplied to a motor is reduced during start-up, the starting torque generally decreases. This reduction occurs because torque in most electric motors, such as an induction motor, is proportional to the square of the applied voltage. Therefore, if the voltage is diminished, the torque generated at start-up becomes less effective.

The relationship between voltage and torque can be understood through the equation for torque, which states that torque is a function of the current and the magnetic field strength, both of which are influenced by the operating voltage. Lower voltage results in lower current, and as a consequence, the magnetic field strength is reduced. This means the overall torque produced at start-up declines, leading to insufficient torque to overcome inertia and start the motor effectively.

Consequently, when facing a scenario where the voltage is lowered, it is accurate to assert that the starting torque decreases, making this the correct answer.