1) describe in detail about energy in magnetic system.

2)(a) With one ex derive the co-energy of a multi excited magnetic field system.

(b) two coupled coils have self and mutual inductance of

L11 = 3+0.5 x ;L22 = 2+0.5x ; L12= L21=0.3x

Over a certain range of linear displacement x. The first coil is excited by a constant current of 15A and the second by a constant current of -8A.

(i) Mechanical work done if x changes from 0.6 to 1m

(ii) Energy supplied by each electrical source in part 1

3)(a) With neat sketch describe the multiple excited magnetic field system in electromechanical energy conversion systems. Also obtain the expression for field energy in the system.

(b) Draw and describe the general block diagram of an electromechanical energy conversion device.

4) Two coupled coils have self and mutual inductance of L11=2+1/(2x); L22=1+1/(2x):

L12= L21=1/(2x). Over a certain range of linear displacement x. The first coil is excited by a constant current of 20A and the second by a constant current of -10A.

(i) Mechanical work done if x changes from 0.5 to1m

(ii) Energy supplied by each electrical source in part 1

(iii) Change in field energy in part1
Hence verify that the energy supplied by the sources is equal to the increase in field energy plus the mechanical work done.

5) Consider an attracted armature relay is exited by an electric source. describe about the mechanical force developed and the mechanical energy output with necessary equations. For linear and non linear cases.