EE Mid

Question 1

The zero sequence component of the unbalanced 3-phase system of vectors VA, VB, and VC is ______ of their vector sum.

Answer 1

one third

Question 2

In most generators, the output voltage is induced by?

Answer 2

relative motion between the field and the armature coils

Question 3

Wave winding is employed in a dc machine of?

Answer 3

low current and high voltage rating

Question 4

The function of an equalizer ring is? (2)

Answer 4

1. To avoid unequal distribution of current at brushes.
2. To help get sparkless commutations

Question 5

The teeth in the armature of a DC machine are sometimes skewed. This is done to reduce?

Answer 5

Vibrations

Question 6

A quantity that contains all the power information in a given load is the?

Answer 6

Complex Power

Question 7

Transient disturbance is produced in a circuit whenever… (3)

Answer 7

1. It is suddenly connected or disconnected from the supply.
2. It is shorted.
3. Its applied voltage is changed suddenly.

Question 8

There are no transients in pure resistive circuit because they…

Answer 8

have no stored energy

Question 9

Transient currents in electrical circuit are associated with… (2)

Answer 9

1. inductors
2. capacitors

Question 10

It is the name given to that property of a material which opposes the creation of magnetic flux in it. It, in fact, measures the opposition offered to the passage if magnetic flux through a material.

Answer 10

Reluctance

Question 11

It is a property that implies the case or readiness with which magnetic flux is developed.

Answer 11

Permeance

Question 12

Kirchhoff’s current law is applicable to only…

Answer 12

junctions in a network

Question 13

Maxwell’s loop current method of solving electrical networks…

Answer 13

utilizes kirchhoff’s voltage law

Question 14

One kWh of electric energy equals?

Answer 14

860 kcal

Question 15

The unit of absolute permittivity of a medium is?

Answer 15

farad/meter

Question 16

In parallel resonance, what will happen to the current?

Answer 16

Minimum

Question 17

Between no-load and full-load, ________ motor develops the least torque.

Answer 17

series

Question 18

The shaft torque of a DC motor is less than its armature torque because of ___________ losses.

Answer 18

rotational

Question 19

What DC motor would be suitable for drives requiring high starting torques but inly fairly constant speed such as crushers?

Answer 19

compound

Question 20

A 200V, 10A motor could be rewound for 100V, 20A by using _____ as many turns per coil of wire, having _____ the cross-sectional area.

Answer 20

half, twice

Question 21

Unlike a shunt motor, it is difficult for a series motor to stall under heavy loading because? (2)

Answer 21

• it develops high overload torque
• it slows down considerably

Question 22

The quantity which maintains the same direction whether a DC machine runs as a generator or as a motor.

Answer 22

Field Current

Question 23

In a DC motor, the mechanical output power actually comes from?

Answer 23

electrical input power

Question 24

These are produced when the energized circuit is rapidly de-energized and reaches an eventual steady-state of zero current or voltage, as in this case of short-circuiting an RL or RC circuit suddenly.

Answer 24

Subsidence Transients

Question 25

In these transients, the transition occurs cyclically towards states, which when reached, become unstable themselves.

Answer 25

Relaxation Transients

Question 26

A smooth output from a generator is obtained by?

Answer 26

design of the armature winding

Question 27

In a DC machine, stray loss is the sum of?

Answer 27

Iron loss and Mechanical loss

Question 28

A DC generator works on the principle of?

Answer 28

Faraday’s Law of Electromagnetic Inductuon

Question 29

These are produced in a circuit, which is originally dead, is energized.

Answer 29

Initiation Transients

Question 30

These are produced in a circuit which is simultaneously subjected to two transients due to two independent disturbance or when the disturbing force producing the transients is itself variable.

Answer 30

Complex Transients

Question 31

Transient current in an RLC circuit is oscillatory when

Answer 31

R<2sqrt(L/C)

Question 32

The transient current in a loss-free LC circuit when excited from an AC source is a/an _______ sine wave.

Answer 32

undamped

Question 33

Double energy transients are produced in circuits consisting of… (3)

Answer 33

1. resistance
2. inductance
3. capacitance