Select the correct answer from the given options.

For traction work, the motor used is

Induction motor

DC Series motor

DC Shunt motor

Synchronous motor

In case of transformer, the frequency of output supply is

equal to that of input supply

greater than input supply

less than input supply

Cannot be said

For maximum power transfer to the load, the condition required is

RL 2 Rs

RL =Rs

RL Rs 2

RL 4 Rs

In a capacitive circuit, power factor is

1

leading

lagging

0.8 always

Long distance power transmission is always preferred due to

less line power loss

less conductor size required

less voltage drop along the line

All the above

The equivalent resistance across AB in Figure 1 is

<img src='./qimages/15287-1f.jpg'>

1 ohm

4 ohm

6 ohm

2 ohm

The unit of capacitive reactance is

Henry

Ohms

Farad

Curie

Write True or False for the following statements:

DC generator does not contain commutator.

Hysteresis losses occur in diamagnetic materials.

The voltage between two phases of a three phase supply is called line voltage.

3-phase induction motor always operates at unity power factor.

Lap winding is used in induction motor.

Only one kind of flux is associated with alternator.

A synchronous machine has both stator and rotor.


Find the equivalent resistance between the terminals A and B in Figure 2. Every arm of the cube has a resistance of 2 ohm.

<img src='./qimages/15287-2a.jpg'>

State and prove maximum power transfer theorem for a dc network.

Draw the Thevenin's equivalent of the circuit shown in Figure 3 across points A and B. Also calculate the current flowing through branch AB.

<img src='./qimages/15287-3a.jpg'>

State and explain Norton's theorem with the help of a suitable example.

Explain the concept of armature reaction in a dc machine.

Draw the various characteristics of a dc generator.

Derive the emf equation of a transformer.

Draw and discuss the equivalent circuit of a transformer.

Discuss the torque-slip characteristics of a 3-phase induction motor.

Draw the circuit diagram of an auto transformer starter and give its advantages and disadvantages.

Explain the working principle of an alternator.

With the help of a diagram, explain the working principle of a synchronous motor.