Introduction:
A two-phase servomotor is a type of electric motor that is commonly used in various industrial applications. It consists of two windings placed at a 90-degree electrical angle to each other. These windings are energized with an AC current to produce a rotating magnetic field, which interacts with the rotor to generate torque and rotation.

Explanation:
The given question asks which statement is not correct for a two-phase servomotor. Let's analyze each option:

a) Rotor diameter is small:
The rotor diameter of a servomotor is not directly related to its type. It can vary depending on the specific application and design requirements. Therefore, the statement that the rotor diameter is small or not small cannot be universally applied to all two-phase servomotors. Hence, this statement is not incorrect for a two-phase servomotor.

b) Applied voltages are seldom balanced:
In a two-phase servomotor, the applied voltages to the two windings are typically not balanced. This is because the windings are energized with different voltages and phases to create the desired magnetic field. The unbalanced voltages help in achieving the desired torque and rotation characteristics. Therefore, this statement is correct for a two-phase servomotor.

c) Rotor resistance is low:
The rotor resistance of a servomotor determines its torque characteristics. A low rotor resistance allows for better control and responsiveness of the motor. In a two-phase servomotor, the rotor resistance is typically low to improve its dynamic performance and efficiency. Therefore, this statement is correct for a two-phase servomotor.

d) Torque speed curve is linear:
The torque-speed curve of a motor represents the relationship between the torque produced by the motor and its rotational speed. In a two-phase servomotor, the torque-speed curve is typically nonlinear. It exhibits a peak torque at a specific speed and decreases as the speed increases or decreases from that point. This nonlinearity allows for precise control and positioning of the motor. Therefore, this statement is not correct for a two-phase servomotor.

Conclusion:
Based on the analysis, the statement that is not correct for a two-phase servomotor is option 'd) Torque speed curve is linear'. The torque-speed curve of a two-phase servomotor is typically nonlinear, exhibiting a peak torque at a specific speed.