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Electrical > ELV Single Path Circuits > Flashcards

ELV Single Path Circuits Flashcards

1
Q

What does the typical electrical grid look like ?

A
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2
Q

What is the typical structure of an atom ?

A
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3
Q

What is the difference btw conventional current flow and electron current flow ?

A

Conventional current = from +ve to -ve

Electron current = from -ve to +ve

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4
Q

What is static electricity ?

A

Static electricity form as a result of an imbalance in electrical charges on the surface of a material.

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5
Q

Explain the fundamental process that makes lightning static electricity.

A
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6
Q

What is Quantity of electricity ?

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7
Q

what is this symbol ?

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8
Q

what is this symbol ?

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9
Q

what is this component ?

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10
Q

what is this component ?

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11
Q

what is the basic arrangement of a circuit ?

A
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12
Q

what happens to the total resistance in an open circuit?

A

Resistance becomes infinity.

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13
Q

what happens to the total resistance in an short circuit?

A

Total resistance is reduced.

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14
Q

What is electrical power ?

A

Electrical power can be defined as the rate at which electrical energy is converted into another form of energy (e.g. light, heat, mechanical).

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15
Q

List the 3 electrical power equation.

A
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16
Q

What is electrical energy ?

A

Energy can be defined as the capacity to expend power over a period of time.

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17
Q

what is work ?

A

Work can be defined as a measure of force applied over a distance.

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18
Q

In what electrical terms are electrical appliances rated ?

A

Voltage and output power

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19
Q

What does the power rating of a resistor indicate ?

A

The power rating of a resistor indicates the maximum amount of heat it can dissipate continuously without causing damage.

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20
Q

What does the power rating of electrical equipment indicate ?

A

The power ratings of electrical equipment indicate their maximum output power

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21
Q

Calculate the maximum voltage that can safely be applied to a 45 Ω resistor that has a power rating of 5 W.

A

If a voltage greater than 15 V is applied, the heating caused by the resulting current would damage the resistor.

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22
Q

The physiological effects of electric current on the human body depends on ?

A

The magnitude of the current.
The duration of exposure.
The path of the current through the body.
Whether the current is alternating (a.c.) or direct (d.c.).

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23
Q

Explain the different zones in the shock chart

A
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24
Q

List some examples of magnetic effect of current

A

Alternators and generators.
Electric motors.
Transformers.
Relays and contactors.

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25
Q

What is heating effect of current ?

A

Occurs as a result of the work done to overcome the resistance of the conductor.
Eg>
Heating elements.
Spot welding.
Arc welding.

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26
Q

What is chemical effect of current ?

A

Occurs when current flows in an electrolyte that is in contact with two or more dissimilar metals. An electrolyte is a liquid that conducts electric current by the movement of ions.

Eg>
Battery charging.
Electroplating.
Refining metals.

27
Q

What are the 3 fundamental risks in electrical installation?

A

Shock current.
Excessive temperatures.
Explosive atmospheres.

28
Q

What is corrosion ?

A

Is the deterioration of a metal due to a chemical reaction called ‘oxidation’

29
Q

What are the 3 mechanisms by which metals can corrode ?

A

Galvanic corrosion.
Atmospheric corrosion.
Microbial corrosion.

30
Q

What is Galvanic Corrosion ?

A

Galvanic corrosion occurs when an electrolyte (such as water) allows the movement of ions from one dissimilar metal to another. This causes the more reactive metal to deteriorate at an accelerated rate and the less reactive metal deteriorate at a reduced rate.

31
Q

What is atmospheric corrosion ?

A

Atmospheric corrosion occurs when a metal is exposed to an oxidizing agent in the environment (such as oxygen).

32
Q

What is Microbial Corrosion ?

A

Microbial corrosion occurs when certain types of microorganisms are present on a metal. The microorganisms produce oxidizing or acidic byproducts that cause the metal to degrade.

33
Q

What is Electromagnetic induction?

A
34
Q

What is Thermocouple Effect ?

A
35
Q

What is the Piezoelectric Effect ?

A
36
Q

What is this cell ?

A

Primary secondary cell

37
Q

What is this cell

A

Hydrogen fuel cell

38
Q

What is electrical power efficiency ?

A
39
Q

What is a fixed resister and list the types .

A
40
Q

What resistor is this ?

A
41
Q

What resistor is this ?

A
42
Q

What resistor is this ?

A
43
Q
A
44
Q

What is a variable Resistor ?

A

A variable resistor is designed in such a way that the resistance can be changed manually. It resistor has two fixed contacts attached to the ends of a resistive strip and a ‘wiper’ contact that can be adjusted to vary the resistance between the fixed and wiper terminals.

45
Q

What is the name of this variable resistor ?

A

Carbon-film Variable Resistor

46
Q

What is the name of this variable resistor ?

A

Wire-wound Variable Resistor

47
Q

What are the 2 primary types of variable resistors ?

A

Potentiometers.
Rheostats.

48
Q

What is the purpose of Potentiometer connection ?

A

The purpose of a potentiometer is to provide voltage adjustment. A typical application for a potentiometer is to provide volume control on audio equipment.

49
Q

what does this graph indicate ?

A

The relationship between the resistance and the wiper position can be either linear or logarithmic:

For a linear resistor, the change in resistance is directly proportional to the physical adjustment.
For a logarithmic potentiometer, the change in resistance is not directly proportional to the physical adjustment.

50
Q

What is the purpose of a Rheostat connection ?

A

The purpose of a rheostat is to provide current adjustment. They come in a range of power ratings for low and high power applications, including motor control (high power), and various electronic equipment (low power)

51
Q

What are non linear resistors ?

A

The resistance of a non-linear resistor varies depending on an external factor, such as temperature, voltage or illumination. The term ‘non-linear’ means that the relationship between the resistance and the external factor are not directly proportional.

52
Q

List 3 types of non linear resistors.

A

Varistors.
Thermistors.
Light dependent resistors (LDRs).

53
Q

What resistor is this ?

A

Varistor

54
Q

Describe the characteristics and uses of varistor.

A

A varistor consists of two electrodes separated by a metal-oxide layer. The metal-oxide offers a very high resistance until the applied voltage reaches a certain level, at which point the resistance drops sharply.

Metal-oxide varistors are commonly used as overvoltage (surge) protection devices.

55
Q

What resistor is this ?

A

Thermistor

56
Q

Describe the characteristics and uses of thermistor.

A

Consists of two electrodes separated by a ceramic or polymer layer. There are two types of thermistor:

Positive Temperature Coefficient (PTC) thermistors. – Resistance increase with increasing temp

Negative Temperature Coefficient (NTC) thermistors. – Resistance increase with decreasing temp

used for motor protection and temperature sensing.

57
Q

what resistor is this ?

A

Light dependent resistor (LDR)

58
Q

Describe the characteristics and uses for LDR.

A

(LDR) consists of two electrodes separated by a cadmium sulphide track. The cadmium sulphide track offers a very high resistance when not exposed to light, and a very low resistance when illuminated.

commonly used in lighting control systems, for example to automatically switch street lighting at dawn and dusk.

59
Q

Memorize the resistor color code diagram.

A
60
Q

What are the preferred resistor values ?

A

A system of ‘preferred resistor values’ was implemented to facilitate manufacture and selection of resistors. The system involves a number of standardised series of resistor values, where each series contains resistors of a specific tolerance. There are 5 main series in use today:

E12 Series (10% tolerance).
E24 Series (5% tolerance).
E48 Series (2% tolerance).
E96 Series (1% tolerance).
E192 Series (<1% tolerance).

61
Q

Use of resistor notation.

A
62
Q

In a series circuit, the total power dissipated = ?

A

The sum of individual powers

63
Q

what happens to the total resistance under open circuit fault conditions ( in single path circuits ) ?

A

Total resistance to become infinite

64
Q

what happens to the total resistance under short circuit fault conditions ( in single path circuits ) ?

A

Total resistance is reduced.

Electrical (7 decks)

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