When a dual-voltage 3Ø motor is connected to a 480-volt circuit, how does the current compare to when connected to a 240-volt circuit?

When a dual-voltage 3-phase motor is connected to a circuit, the current it draws is influenced by the voltage applied and the load it is driving. In this scenario, when a motor is running at a higher voltage, such as 480 volts compared to 240 volts, the fundamental relationship defined by Ohm's law and the power equation informs us about the current draw.

For motors, power is calculated as the product of voltage, current, and the square root of 3 in a three-phase system. Therefore, for a given power demand, if you increase the voltage, the current must decrease proportionally to maintain the same power output. This means that if the motor is rated for a specific amount of power regardless of how you connect it (to either voltage), when it is connected to a higher voltage source, it draws less current than when connected to a lower voltage source for the same power output.

This relationship inherently shows why the correct answer indicates that the current drawn by the motor at 480 volts is less than when it is connected to a 240-volt circuit. It reflects the nature of electrical power systems where increasing voltage reduces current for a constant power requirement, attributed to the efficiency and design of motors and electrical circuits.