Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

Electrical Definitions > Chapter 2 Cables and conductors > Flashcards

Chapter 2 Cables and conductors Flashcards

(70 cards)

Start Studying
1
Q

What is a conductor?

A

A conductor is a material which offerrs a low resistance to a flow of current.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Everyday conductors must be of

A

Low electrical resistance

Mechnically strong and flexible

and relatively cheap

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

An insulator is?

A

An insulator is a material which offers a very high resistance to a flow of current

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What should an insulator have ?

A

Certain electrical,mechanical,physical and chemical properties

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Electrical properties

A

Must have a high resistance

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Mechnical properties

A

It must be capable of withstanding mechnical stress like compression

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Physical properties

A

non- absorbent and capable of withstanding high temperatures

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Chemical properties

A

withstanding corrosive effects of chemicals

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Types of insulators ?

A

Rubber, pocelain,polyvinyl chloride paper , wood, plastic

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Types of conductors are?

A

Gold, sliver, copper, iron ,aluminium

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

A cable is

A

A length of insulated conductor or group of conductors used to carry current

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Two basic parts of cable?

A

Conductor and Insulator

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Types of Cables

A

Polyvinyl chloride cable
Multi- core cable
tough - rubber sheathed
Earth continuity conductor cable

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Note:

A

The current rating in a cable decreases as temperature increases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

The current density

A

The amount of current which the conductor can safely carry without heating per unit cross sectional area.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

The resistance that a conductor offers are determined by

A

The length of conductors
cross - sectional area
Type of material etc

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Temperature coefficient:?’

A

This is for coeffient of a material is the increase in the resistance of , 1ohm of that material when it is subject to the rise of temperature.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Positve temperature coefficient

A

copper and aluminium resistance/ increases as temp increases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Negative temperature coefficient

A

Carbon and electrolytes /resistance decrease as temp increase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

resistivity

A

The resistance of unit cube of a material measured on opposite faces of a cube= pL/a

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Temperature coefficient

A

R2/R1 = 1 + 0.004 x 30
= 1 + 0.004 x 20

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

When is trunking used

A

In conditions where the cables are too large for using conduit

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Resistance

A

The friction a material presents to a flow of current

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Voltage Drop -

A

The reduction in voltage in a circuit

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Domestic installation
supplied from a 16mm2 three coree amoured cable
26
Note :
Trucks and ducts must be fixed and protected against corrosion
27
temporary installation
an installation with an expected period of three months
28
A circuit
a group of conductors for the purpose of carrying curent
29
Consumer's terminals
The point of connection of the consumers' conductors to the supply Authority meter .
30
Purpose of testing an installation
To dectect faults in the installation before dangerous situations arisen
31
types of protection
Elecromagnet Fuse Thermal
32
Final sub circuit
connected to the distrubution board to supply electrical energy
33
A installation needs to be protected from
Eaarth leakage , danger of electric shock, excess current and corrosion
34
Electrical installation test
Visual inspection of workmanshop. Verification of polarityi Insulation resistance test Testing for effective grounding Continuty test
35
what is a tool?
ppowered by human muscles rather than motors and engines
36
why do you put switch gear in an installation
To protect cuircuits against excess current , earth leakage
37
Note:
If a current passed through a conductor, the temperature of that conductor increases
38
Units of electrical energy
The joule (J) and kilo-watt-hour (kWh)
39
Joules =
Watts x seconds
40
Kilowatt
energy consumed when one kilwatts is used for one hour. 1 kWh = 3,600,000J
41
to convert 0f to 0c subtract 32 and multiply by 5 /9
to convert 0c to 0f multiply by 9/5 and add 32
42
Wattmeter
measures the electrical power in a circuit
43
ohm meter
The ohm is used to measure smaller values of resistance
44
NOTE
If a current passes through a coil an electromagnet will be produced
45
Difference between single bell and trembler
the trembler has a set of variable contacts
46
types of indicator element
1) The pendulum type element 2) mechanical replacement type element 3)electrical replacement type element
47
Purpose of the electric cell is?
To .change chemical energy into electrical energy
48
Electrolyte
A liquid which changes its composition when a current passes through it
49
Simple Lechanche Cell
Glass container Electrolytes - sal ammoniac Carbon plate - (+ ve electrode) Zinc plate - (+ ve electrode)
50
Leclanche cell has two main faults
Local action and polarization
51
Local action
corroding of electrode
52
Polarization
hydrogen bubbles resisting flow of current
53
two modification Leclanche cells
Zinc electrode coated with mercury carbon plate +ve surrounded with depolarising agent
54
A Lechanche is termed primary cell when?
because it cannot be recharged chemically
55
Advantages and disadvantages Leclanche
adv - (1) Cheap requires little maintainance disadv - It is not portable in the form cell cannot be used over and over again .
56
Effects of polarization
Incapable of supplying heavy currents Having a high internal resistance
57
Lead- Acid cells
is secondary because it can be charged electrically
58
Methods of charging batteries
Trickle charge Constant current Constant Voltage Floating system
59
precaution
Always add acid to water not water to acid Fire-fighting appliances should be handyd room must be well ventilated
60
Find internal resistance
subtract the closed curcuit voltage from open circuit voltage and divide by circuit current r= E-V/I
61
What is a service line?
Any electric conductor through which energy is supplied by the commission to the consumer
62
Raceway
An enclosed channel that forms the path of electrical conductors to prevent them from heat moisture and dust
63
Advanatages of using EMT over PVC
1)EMT is more durable than PVC 2)EMT is fire resistant where as pvc isn't 3)EMT has high mechanical strenth where as pvc has physical weakness
64
Differences between a circuit breaker and fuse
1)Circuit breakers short circuit when there is an overload in current whereas fuses melt 2)Circuit breaker can be reused over again whereas fuse is a one time use 3) Circuit breaker are safer than fuse because its a flip of a switch 4)Circuit breakers do not have exposed live parts where as fuses do
65
Effects of loose termination on a busbar
1)The current would not be able to effectively return to supply causing overheating 2) There will be a break or short circuit if connection fails 3)The electrical apparatus can be destroyed
66
How high voltages from t and tec is reduced for supply to residential ?
Transmission - To step up the voltages to be transmitted over long distances Distribution - To stepdown the voltage to be distributed to consumers from substation
67
Relationships between protective device and circuit conductors
If there is an overload of current the protective device automatically short circuits stopping the flow of current.
68
Raceway types
Conduct or trunking ducting
69
Space factor
Space factor is the ratio of the space occupied by the cables to the total space inside the conduit.
70

Electrical Definitions (3 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions