For good performance the small dc motor should have magnetic to electrical boarding ratio greater than 70.

For optimal performance, a small DC motor should indeed maintain a magnetic to electrical loading ratio greater than 70. This ratio is important because it influences the efficiency and performance of the motor. Magnetic loading refers to the flux per pole (total flux divided by the number of poles) in the motor, while electrical loading refers to the current per meter of armature perimeter.

A higher ratio indicates a motor design that is more efficient in its conversion of electrical energy into mechanical energy, leading to better overall performance. It suggests that the motor is effectively utilizing its magnetic circuit, which reduces losses and improves output. This ratio is a key factor in motor design, affecting size, cost, and efficiency. Correctly balancing these loadings is essential for achieving desired motor performance, especially in applications where space and efficiency are critical.