Question

The force produced by electric field in a singly excited energy conversion device, using electric field as coupling medium can be obtained by ___________

(a) use of field energy function only

(b) use of coenergy function only

(c) use of field energy or coenergy function

(d) none of the mentioned

This question was posed to me in unit test.

My enquiry is from Singly Excited Electric Field Systems topic in section Basic Concepts in Rotating Machines of Electrical Machines

Answer 1

Correct answer is (c) use of field energy or coenergy function

The explanation is: fe = -∂Wfld(q,x)/∂x

fe = -∂Wfld^1(q,x)/∂x.