Midterms

Question 1

does not create energy. It changes mechanical energy into electrical energy.

Answer 1

Generator

Question 2

The outer frame of a dc machine is called as ______\. It is made up of cast iron or steel.

Answer 2

Yoke

Question 3

serve two purposes; they spread out the flux in the air gap and also, being of larger cross- section, reduce the reluctance of the magnetic path they support the exciting coils (or field coils).

Answer 3

Poles and Pole Shoes

Question 4

They are usually made of copper. Field coils are former wound and placed on each pole and are connected in series.

Answer 4

Field Winding

Question 5

is the rotor of a dc machine. It is cylindrical in shape with slots to carry armature winding.

Answer 5

Armature Core

Question 6

It is usually a former wound copper coil which rests in armature slots.

Answer 6

Armature Winding

Question 7

consists of a set of copper segments which are insulated from each other.

Answer 7

Commutator

Question 8

They rest on commutator segments and slide on the segments when the commutator rotates keeping the physical contact to collect or supply the current.

Answer 8

Brushes

Question 9

Brushes are usually made of

Answer 9

Carbon or Graphite

Question 10

are those whose field magnets are energized from an independent external source of DC current.

Answer 10

Separately Excited Generators

Question 11

are those whose field magnets are energized by current produced by the generators themselves.

Answer 11

Self Excited Generators

Question 12

the field windings are connected across or in parallel with the armature conductors and have the full voltage of the generator applied across them.

Answer 12

Shunt Wound

Question 13

the field windings are joined in series with the armature conductors

Answer 13

Series Wound

Question 14

: it is a combination of a few series and a few shunt windings

Answer 14

Compound Wound

Question 15

Compound Wound can be:

Answer 15

Short shunt or Long shunt

Question 16

is a type of electric machine that converts electrical energy into mechanical energy.

Answer 16

DC Motor

Question 17

DC motors include two key components

Answer 17

a field coil or stator or permanent magnet and an armature or rotor.

Question 18

is an AC (alternating current) device that transfers power from one circuit to another without a rotating part and change of frequency.

Answer 18

Transformer

Question 19

IT WORKS ON THE PRINCIPLE OF

Answer 19

MUTUAL INDUCTION

Question 20

– is the basis of a transformer between two circuits linked by a common magnetic flux.

Answer 20

Mutual Induction

Question 21

work with electromagnets and discover the property of induction independently on separate continents.

Answer 21

Joseph Henry and Michael Faraday

Question 22

invents the
induction coil.

Answer 22

Rev. Nicholas Callan of Maynooth College

Question 23

uses induction coils in his lighting system

Answer 23

Pavel Yablochkov

Question 24

uses induction coils in their lighting systems with AC incandescent systems.

Answer 24

The Ganz Company

Question 25

designs one of the earliest AC power systems with William Thomson (Lord Kelvin). He creates an early transformer.

Answer 25

Sebastian Ziani de Ferranti

Question 26

first built a “secondary generator” or in today’s terminology a step down transformer which they designed with open iron core, the invention was not very efficient to produce. It had a linear shape which did not work efficiently.

Answer 26

Lucien Gaulard and John Dixon Gibbs

Question 27

is a type of transformer with the function of converting low voltage (LV) and high current from the transformer’s primary side to high voltage (HV) and low current value on the transformers’ secondary side.

Answer 27

The step-up transformer

Question 28

is a type of transformer that converts high voltage (HV) and low current from the primary side of the transformer to low voltage (LV) and high current value on the secondary side of the transformer.

Answer 28

The step-down transformer

Question 29

The structure of core of this transformer is in the form of a rectangular frame made from cold rolled grain oriented sheet steel (C.R.G.O.) with thin silicon steel laminations.

Answer 29

Core-type construction

Question 30

the magnetic circuit (core) surrounds a considerable portion of the windings.

Answer 30

Shell-type construction