1.a. Write the expression for the mechanical force developed by the magnetic field for a nonlinear case.

1.b. Why energy stringing capacity of magnetic field is much larger than the electric field.

1.c. State the salient feature of simplex winding.

1.d. What is the action of commulator and brushes of a.d.c machine.

1.e. Define critical field and critical speed of a.d.c generator.

1.f. Write the condition necessary for the voltage build-up in DC generator.

1.g. A d.c shunt motor is connected to a 3-point starter. Explain what would happen if the field circuit become open circuit with the motor running at no-load.

1.h. Draw the circuit model for ward-leonard system of speed control.

1.i. State with reason whether field test on two identical DC series machines is regenerative method?

1.j. Write the expression for core losses and remedial measures to reduce them in a DC Machine.

2.a. What is meant by singly-excited and Dolby-excited electromechanical energy conversion? Give two example of each.

2.b. The self and mutual inductance of two exciting coils of multiply excited translator system are: L11= L12=3.6/1+2x) L12= L21=1.8=/(1+2x) Calculate the time average force and coil current at X=0.3m when both the square car connected in parallel across a voltage source of 100cos314t.

3.a. With one example derive the co-energy of multi excited magnetic field system.

3.b. What are the cause for irrrecoverable energy loss when the flux in the magnetic circuit undergoes a cycle?

4. Explain the effect of armature reaction in a DC shunt generator. How is it demagnetizing and cross magnetizing ampere turns calculated?

5.a. Draw the sketches for different method of excitation of DC generator and write the respective generated emf equation.

5.b. A d.c machine has 8 poles, lap connected armature with 960 conductors and flux per pole is 40 mWb. It's driven at 400 r.p.m. Calculate the generated emf. If now lap connected armature is replaced by wave connected, calculated the speed at which it should be able to generate 400V.

6. Discuss the constructional details and working principle of 2-pole and 4-pole D.C machines. Also discuss the performance characteristics of d.c generator.

7.a. State the application of various type of generators according to their characteristies.

7.b. Two DC shunt generator are connected in parallel to supply a load of 500A. Each machine has an armature resistance of 0.3$\Omega$/ and field resistance of 60$\Omega$/ but the EMF of one machine is 600V and that is the other machine is 640V. What power does each machine supply?

8. What is the necessary of starter in a DC motor? Explain the working principle of 3-point starter with neat sketch. Also explain about protective measure in the starter.

9.a. Enumerate the factors on which speed of a D.C. motor depends. Explain briefly about speed control method of DC motor.

9.b. A d.c motor take an armature current of 74 A when flux is 10 mWb. it develops a torque of 120N-m if armature current is changed to 45A keeping the flux constant, determine the new torque developed. With the same flux if entire load is on the motor is removed. Armature current is observed to be 6.8 A. Determine the torque required to overcome stray losses.

10. With the help of neat circuit diagram explain swinburne's test and derives the relation for efficiency (both for generator and motor) also state the merit and demerit of this method.

11. With the help of neat circuit diagram explain Hopkinson's test and derives the relation for efficiency (both for generator and motor) also state the merit and demerit of this method.