Electric Motor efficiency

It would make some sense to say that the sum of active area (coil to magnet) would influence the total output, especially if this area covers the shaft's length, but efficiency is dependant on the type of technology applied. To some degree it is known for instance, that DC motors are more efficient than AC motors, or that electrical motors are more efficient than internal combustion engines, but then again you would have to agree on what is included to define efficiency.

For example: If it's the total chemical (caloric) potential compared to a usable mechanical torque, you would say that an internal combustion engine has a mere 35 to 45 percent efficiency, which sounds awful, even if no potential loss is present, due to friction, heat loss, through the conversion of linear to angular momentum, etc. If this is to be compared to given DC motor efficiency of 85 to 95 percent, you may be inclined to favour electrical.

But, can you apply it through practical means? Remember that the efficiency and capacity of the battery used, is a main factor in this "efficiency calculation" being a main integral part of the circuit.

Efficiency is subject to your manner of definition.

A new type of ultra-high efficiency electric motor which is now commercially available changes the rules. A rotating copper disc uses small, induced current loops to produce regional magnetic fields, which in turn interact with sequenced exterior magnetic fields to produce rotational motion. Variable speed with very high starting torque is the result. The motor looks like a pancake.

This may sound nuts: what you just described sounds like a linear motor, looped back into a circle.

By the way: Back in 2003 I read Renault prototyped an electric lorry, with 4 motors, each as a wheel.