If in a synchronous motor, driving a given mechanical load and drawing current at a leading power factor from constant voltage supply its field excitation is increased, its power factor

The correct answer is A.

When the field excitation of a synchronous

motor is increased, the motor’s magnetic field becomes stronger. This causes the motor to draw more current from the supply, and the power factor of the motor becomes more leading.

A leading power factor

is desirable in many applications, as it means that the motor is helping to improve the overall power factor of the system.

Option B is incorrect, as increasing the field excitation will cause the motor to draw more current, not less.

Option C is incorrect, as increasing the field excitation will cause the power factor to become more leading, not remain unchanged.

Option D is incorrect, as the correct answer is A.