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City And Guild Second Edition: for the Level 3 Apprenticeships (5357 and 5393), Level 3 Advanced Technical Diploma (8202), Level 3 Diploma (2365): > Advanced scientific principles > Flashcards

Advanced scientific principles Flashcards

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1
Q

What major changes occurred in the English electricity industry in 1990?

A

Privatisation of the 12 regional electricity boards

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2
Q

Which of the following organisations owns and operates power stations that generate electricity from various sources?

A

Generators

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3
Q

What is the primary role of the Transmission System Owner in the UK power system?

A

Owning and maintaining the high-voltage transmission system

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4
Q

How does the system operator balance electricity demand and generation output?

A

By asking generators to increase output

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5
Q

What is distributed generation (DG) in the power system context?

A

Generation connected to the distribution network

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6
Q

In a three-phase AC generator, how are the windings on the stator arranged to produce a three-phase output?

A

Windings are connected in a star configuration

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7
Q

What is the purpose of step-up transformers in the UK power system?

A

To increase the voltage for long-distance transmission

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8
Q

Which type of electricity generation method is known for its ability to produce electricity without significant transmission losses over long distances?

A

High Voltage Direct Current (HVDC)

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9
Q

What is the primary source of heat for most electricity generation methods in the UK?

A

Fossil fuels and nuclear fission

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10
Q

What is the purpose of combined heat and power (CHP) generation systems?

A

To maximize waste heat by using it for heating or production processes

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11
Q

What is the term for a chemical solution that contains many ions and is used in battery production?

A

Electrolyte

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12
Q

Which two companies took over the CEGB’s big coal-fired power stations in 1991 in the UK?

A

National Power and Powergen

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13
Q

In the UK, which organization is responsible for the transportation of electricity between power stations and from region to region?

A

National Grid

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14
Q

What type of electricity generation method uses the Sun’s heat energy transferred to fluids to produce electricity?

A

Solar thermal

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15
Q

Which type of electricity generation system captures waste heat or thermal energy for heating schemes or production processes?

A

Combined heat and power (CHP)

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16
Q

What is the primary purpose of the interconnectors between the UK and Europe?

A

To pool capacity and diversity of supplies

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17
Q

Which of the following is NOT a current interconnector between the UK and Europe?

A

750 MW between England and Ireland

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18
Q

What type of network carries electricity from primary substations to customers at low voltage levels in urban and rural areas?

A

Secondary distribution network

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19
Q

Which type of transformer is used to decrease the voltage from high voltage transmission systems to a more manageable level for local distribution?

A

Step-down transformer

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20
Q

What is the name for the network of circuits, overhead lines, underground cables, and substations that link power stations and distribute electricity around the country?

A

Power grid

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21
Q

Which of the following is NOT a common voltage supply system used for electricity distribution in work premises?

A

Two-phase AC

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22
Q

In the UK, where is direct current (DC) occasionally used for public electricity supplies?

A

Links between England, the Netherlands, Ireland, and France

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23
Q

What is the primary purpose of DC battery systems in modern installations?

A

To store excess electricity for vehicle charging points

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24
Q

Why is alternating current (AC) the distribution system of choice for electricity suppliers worldwide?

A

AC allows for a wider range of circuit arrangements and supply voltages.

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25
Q

In a single-phase AC supply, what are the two conductors commonly referred to as?

A

Line conductor and neutral conductor

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26
Q

What is the nominal supply voltage for a single-phase AC supply in the UK?

A

230 V

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27
Q

In a balanced three-phase system, why is there no need to have a star-point connection to neutral?

A

The phases have a cancellation effect on each other.

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28
Q

What is the primary advantage of a star (Y) connected load in a three-phase system?

A

It provides a balanced load across all phases.

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29
Q

In a delta (Δ) connected load in a three-phase system, how are the three coil windings connected to each other?

A

In a triangle or delta configuration.

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30
Q

What is the line current (IL) in a delta-connected load if the phase current (IP) is 100 A?

A

173.2 A

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31
Q

Which of the following statements is true regarding neutral conductors in a three-phase AC system?

A

The neutral conductor carries the same current as the line conductors.

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32
Q

In a star (Y) connected load in a three-phase system, what is the relationship between the line current (IL) and the phase current (IP)?

A

IL = IP

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33
Q

Which voltage configuration is commonly used for domestic premises and lighting within work premises in the UK?

A

Single-phase and neutral AC system

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34
Q

What is the primary advantage of using a multi-phase arrangement, such as three-phase, in industrial and commercial premises?

A

It allows for the use of very large conductors.

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35
Q

In a delta-connected load, if the phase voltage (VP) is 400 V, what is the line voltage (VL)?

A

400 V

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36
Q

What is the purpose of a star (Y) connected load in a three-phase system?

A

To ensure a balanced load across all phases.

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37
Q

In a balanced three-phase system, what happens to the star-point voltage naturally?

A

It remains at zero voltage.

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38
Q

Which conductor carries any out-of-balance current in a single-phase load within a three-phase system?

A

Neutral conductor (N)

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39
Q

What does the term “equilateral triangle” refer to when discussing neutral current in a three-phase system?

A

A triangle with sides representing phase currents.

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40
Q

In a delta-connected system, how many wires are used to obtain a three-phase supply?

A

Three wires

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41
Q

What is the purpose of Earth Fault Loop Impedance (Zs) verification?

A

To ensure the safety of electrical installations

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42
Q

Which elements are part of the earth fault current loop in a typical electrical system?

A

Protective conductors and earthing terminals

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43
Q

In TN-C-S systems, what is the typical maximum declared value for earth fault loop impedance external to the installation?

A

0.35Ω

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44
Q

In TN-S systems, how do earth fault loop impedances typically compare to TN-C-S systems?

A

They are higher

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45
Q

In TT systems, why do residual current devices (RCDs) need to be adopted for protection against electric shock?

A

Because they operate at lower earth fault currents

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46
Q

What is the fundamental principle of transformers?

A

Induction of magnetic flux in two coils

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47
Q

Which type of transformer is commonly used for transmitting electrical energy from power stations at high voltages?

A

Power transformer

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48
Q

What is the primary purpose of isolation transformers?

A

To provide electrical separation

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49
Q

Which type of transformer is often used in medical applications to prevent first-fault failures?

A

Isolation transformer

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50
Q

Which type of transformer is used to provide a physical neutral for power transformers with a delta-connected secondary?

A

Earthing transformer

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51
Q

what is the primary function of a step-down transformer in an electrical system?

A

To decrease voltage

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52
Q

In a step-up transformer, the number of turns in the secondary winding is _____ compared to the primary winding.

A

More

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53
Q

What is the primary function of an insulation transformer?

A

To provide electrical separation

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54
Q

Which type of transformer is commonly used for power transmission purposes due to its ability to transmit electricity over long distances efficiently?

A

Power transformer

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55
Q

What is the purpose of the magnetic core in a transformer?

A

To induce a magnetic field

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56
Q

In a current transformer, which winding has only one turn?

A

Primary winding

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57
Q

Which type of transformer is commonly used in domestic bathrooms to power shaver sockets safely?

A

Isolation transformer

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58
Q

What is the typical purpose of earthing transformers in electrical systems?

A

To provide a physical neutral for delta-connected transformers

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59
Q

Which type of transformer is used to measure high currents accurately and is commonly found in electrical metering applications?

A

Current transformer

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60
Q

What is the primary purpose of using thin, insulated laminations in transformer cores?

A

To reduce eddy currents

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61
Q

Eddy current loss in a transformer is primarily a form of which type of loss?

A

Core loss

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62
Q

What is hysteresis loss in a transformer core primarily related to?

A

Magnetization direction changes

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63
Q

What is the main cause of copper losses in a transformer?

A

Resistance in windings

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64
Q

How are copper losses in transformer windings typically calculated?

A

Using the formula I^2R

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65
Q

What is the primary function of an isolation transformer?

A

To provide electrical separation

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66
Q

Which type of transformer is commonly used in electrical metering applications to accurately measure high currents?

A

Current transformer

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67
Q

What type of inductance occurs when a primary winding induces a magnetic field that induces a current into a secondary winding?

A

Mutual inductance

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68
Q

What does the turns ratio of a transformer indicate?

A

The relationship between primary and secondary voltages

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69
Q

How is a transformer typically rated in terms of power?

A

In kilovolt-amperes (kVA)

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70
Q

What is the primary purpose of using laminations in transformer cores?

A

To reduce hysteresis loss

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71
Q

Which type of loss in a transformer core occurs due to the magnetic material’s need to be re-magnetized as the supply alternates direction?

A

Hysteresis loss

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72
Q

What is the primary cause of copper losses in a transformer?

A

Resistance in the windings

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73
Q

In transformers, what is the main factor contributing to core loss?
a) Eddy currents

A

Hysteresis loss

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74
Q

What is the primary function of an isolation transformer in electrical systems?

A

To provide electrical separation

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75
Q

Which type of transformer is commonly used to convert high voltage to low voltage for safe use in households?

A

Self-inductance

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76
Q

What does the turns ratio of a transformer determine?

A

The relationship between primary and secondary currents

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77
Q

How are copper losses in transformer windings related to the load current?

A

Quadratically proportional

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78
Q

In what unit is a transformer’s power rating typically expressed?

A

Kilovolt-amperes (kVA)

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79
Q

What is the primary function of a resistor in an AC circuit?

A
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80
Q

What is the primary function of a resistor in an AC circuit?

A

To restrict current flow proportionally to voltage

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81
Q

In a resistive AC circuit, what is the phase relationship between voltage and current?

A

In-phase (unity)

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82
Q

What types of loads in AC circuits are typically resistive?

A

Incandescent lamps and heaters

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83
Q

What does an inductor primarily introduce in an AC circuit?

A

Inductive reactance

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84
Q

In an ideal inductive circuit, how much does the current lag behind the voltage

A

90 degrees

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85
Q

What is the unit of inductance used to measure inductors in AC circuits?

A

Henry (H)

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86
Q

In a capacitive AC circuit, how does the current phase relationship differ from that in an inductive circuit?

A

Leading current

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87
Q

What is the primary effect of a capacitor in an AC circuit?

A

Leading current

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88
Q

How is capacitive reactance (XC) calculated in an AC circuit?

A

XC = 1 / (2πfC)

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89
Q

What is the primary unit used to measure capacitance in AC circuits?

A

Farad (F)

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90
Q

What is the primary factor that determines the reactance of an inductor in an AC circuit?

A

Frequency of the supply (f)

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91
Q

In an ideal capacitive circuit, what is the phase shift between current and voltage?

A
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92
Q

What is the unit of measurement for reactance in AC circuits, whether inductive or capacitive?

A

Ohm (Ω)

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93
Q

Which type of load is most commonly associated with power factor correction using capacitors?

A

Inductive loads

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94
Q

What is the primary purpose of a transformer in an electrical circuit?

A

To change voltage and current levels

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95
Q

When an AC voltage is applied to a transformer’s primary winding, what is induced in the secondary winding?

A

Voltage

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96
Q

What does the turns ratio of a transformer represent?

A

The ratio of primary to secondary windings

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97
Q

Which component in a transformer is responsible for reducing eddy current losses?

A

Core material

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98
Q

What is the unit used to rate the capacity of a transformer?

A

Volt-amperes (VA)

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99
Q

In what unit is capacitance typically measured?

A

Farad (F)

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100
Q

What is impedance in an electrical circuit?

A

The combination of resistance and reactance (inductive, capacitive, or both)

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101
Q

Which component causes a leading or lagging current in a circuit?

A

Both B and C

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102
Q

How is impedance (Z) calculated in a circuit?

A

Z = R² + X²

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103
Q

In a circuit with both inductance and capacitance, how is the resulting reactance calculated?

A

By subtracting the smaller reactance from the larger

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104
Q

What is the purpose of an impedance triangle in electrical circuits?

A

To visualize the relationship between resistance and reactance

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105
Q

In a series RL circuit, how does the voltage across the components change with respect to the current?

A

Voltage decreases across components

106
Q

What is the phasor sum of voltages in a series RL circuit used to determine?

A

Impedance (Z)

107
Q

In an RLC series circuit, when do the inductive and capacitive reactance cancel each other out?

A

When the circuit is purely resistive

108
Q

When components are connected in parallel in an electrical circuit, what becomes the common component?

A

Voltage

109
Q

What is the total current in a parallel circuit equal to?

A

The sum of currents through each component

110
Q

In an RLC series circuit, what happens to the power factor when the inductive reactance and capacitive reactance cancel each other out?

A

The power factor becomes unity (1)

111
Q

Which formula is used to calculate capacitive reactance (XC) in an AC circuit?

A

XC = 1 / (2πfC)

112
Q

When components in a circuit are connected in series, what happens to the total resistance compared to individual component resistances?

A

It is equal to the sum of the individual resistances

113
Q

In a parallel RL circuit, how does the total impedance (Z) compare to the individual impedances of the resistor and inductor?

A

It is the sum of the impedances of the resistor and inductor

114
Q

What happens to the voltage across components connected in parallel in an AC circuit?

A

It remains constant

115
Q

In an RLC series circuit, if the inductive reactance (XL) is greater than the capacitive reactance (XC), what is the overall phase relationship between current and voltage?

A

Current leads voltage

116
Q

In a parallel RC circuit, what happens to the total current (I) compared to the individual currents through the resistor and capacitor?

A

It is equal to the sum of the individual currents

117
Q

What is the primary purpose of constructing a phasor diagram in AC circuits?

A

To visualize the phase relationships between components

118
Q

In a series RL circuit, if the inductance (L) increases while the resistance (R) remains constant, how does this affect the impedance (Z)?

A

Impedance increases

119
Q

When components in a circuit are connected in parallel, how does this arrangement affect the total resistance compared to individual component resistances?

A

It decreases

120
Q

In a phasor diagram for a parallel circuit, which component serves as the reference line?

A

Voltage (V)

121
Q

In circuits with both series and parallel components, what is often the arrangement for inductance and resistance?

A

Series for inductance and parallel for resistance

122
Q

What is the purpose of a capacitor in a circuit designed for power factor correction?

A

To offset reactive power and improve power factor

123
Q

How is the apparent power related to true power and reactive power in a power triangle?

A

Apparent power is the sum of true power and reactive power

124
Q

What does the power factor represent in an electrical circuit?

A

The cosine of the angle between voltage and current

125
Q

In the example calculation provided, what is the initial power factor rating of the motor before correction?

A

0.4

126
Q

What is the formula for calculating capacitive reactance (XC) in an AC circuit?

A

XC = 1 / (2πfC)

127
Q

What is the significance of a power factor of 1 (unity) in a circuit?

A

It indicates a purely resistive circuit

128
Q

In a series RL circuit, if the inductive reactance (XL) is greater than the resistance (R), what is the phase relationship between current and voltage?

A

Current leads voltage

129
Q

What is the formula for calculating power factor (cosθ) in a circuit using resistance (R) and impedance (Z)?

A

cosθ = R / Z

130
Q

In a phasor diagram for a series RL circuit, which component typically lags behind the other in terms of phase?

A

Inductance (L

131
Q

When determining the impedance of a circuit with both inductive and capacitive components, what value is used for reactance (X)?

A

The difference between inductive and capacitive reactances

132
Q

What is the unit of measurement for apparent power in a power triangle?

A

Volt-amperes (VA)

133
Q

How does the angle between true power and apparent power change when power factor is improved?

A

The angle decreases

134
Q

In a power triangle, what does the angle θ represent?

A

The phase angle between voltage and current

135
Q

In an RL series circuit, if the impedance (Z) is greater than the resistance (R), what is the phase relationship between current and voltage?

A

Voltage leads current

136
Q

What is the formula for calculating capacitive reactance (XC) in an AC circuit?

A

XC = 1 / (2πfC)

137
Q

If the power factor of a circuit is 0.8, what is the angle by which the current lags or leads the voltage?

A

30 degrees

138
Q

In a power triangle, what does the cosine of the angle (cosθ) represent?

A

Power factor

139
Q

What is the power factor of a purely resistive circuit?

A

1 (unity)

140
Q

What does the angle formed by the R and Z lines in an impedance triangle represent?

A

The angle by which the current leads or lags the voltage

141
Q

How is the power factor defined in terms of the impedance triangle?

A

It is the cosine of the angle formed by the R and Z lines.

142
Q

In the given circuit with components in series and in parallel, what is the impedance (Z) value?

A

30.14 Ω

143
Q

What is the formula for capacitive reactance (XC) in the circuit?

A

XC = 1 / (2πfC)

144
Q

What is the power factor of a circuit when the angle of lagging current is 66.55 degrees?

A

0.398

145
Q

Why is power factor correction important in electrical installations?

A

It helps avoid overheating of equipment and cables.

146
Q

What is a common method for power factor correction in electrical installations?

A

Using synchronous motors

147
Q

How is power factor correction typically achieved using capacitors?

A

By adding capacitive kVAr to cancel out inductive kVAr

148
Q

What is load profiling used for in electrical supply monitoring?

A

To monitor times of high demand

149
Q

In a balanced three-phase system, what happens to the star-point voltage?

A

It is naturally at zero current.

150
Q

In an impedance triangle, if the current leads the voltage, what type of circuit is typically present?

A

Inductive

151
Q

How is capacitive reactance (XC) affected when the frequency of the AC power supply increases?

A

XC decreases

152
Q

What is the formula for calculating apparent power (S) in an AC circuit?

A

S = VI

153
Q

What is the angle between the voltage and current in a purely resistive circuit?

A

0 degrees (in-phase)

154
Q

What is the primary purpose of power factor correction equipment in electrical systems?

A

To increase the power factor

155
Q

Which type of equipment is rarely used today for power factor correction in large factories?

A

Synchronous motors

156
Q

What does “kVAr” stand for in the context of power factor correction?

A

Kilovolt-Ampere Reactive

157
Q

How is power factor correction typically achieved in fluorescent luminaires?

A

By connecting capacitors in parallel

158
Q

What does load profiling help electrical systems anticipate?

A

Times of excessive consumption

159
Q

In a balanced three-phase system, what is the relationship between the three phases?

A

They are 120 degrees out of phase.

160
Q

What are the three basic features of DC machines?

A

Magnetic-field system, conductors, and commutator

161
Q

What part of a DC machine is responsible for setting up the magnetic field?

A

Field windings

162
Q

In a DC generator, what is the function of the commutator?

A

To reverse current flow in the armature

163
Q

What type of current does a DC generator produce?

A

Direct current (DC)

164
Q

What is the primary difference between series and shunt DC motors?

A

Shunt motors have a common current for field and armature.

165
Q

Which type of DC motor is known for its ability to be used on both alternating current (AC) and direct current (DC)?

A

Universal motor

166
Q

In a balanced three-phase star-connected system, if the line voltage (VL) is 480 V, what is the phase voltage (VP)?

A

240 V

167
Q

Why is there no need for a star-point connection to neutral in a balanced three-phase star-connected system?

A

Because the current drawn by any one phase is taken out equally by the other two

168
Q

In a delta (Δ) connected load, if the phase current (IP) is 50 A, what is the line current (IL)?

A

100√3 A

169
Q

What is the primary advantage of using a delta-connected system in transmission?

A

Reduced line current

170
Q

Which part of a DC machine is responsible for reversing the direction of current flow in the armature?

A

Commutator

171
Q

What is the main advantage of DC generators over DC motors?

A

DC generators can convert mechanical energy into electrical energy.

172
Q

What is the function of the armature in a DC motor?

A

To convert electrical energy into mechanical power

173
Q

In a compound DC motor, what is the advantage of having both series and shunt field windings?

A

Better speed control

174
Q

Which type of DC motor is commonly used in applications where high starting torque is required, such as electric drills?

A

Series motor

175
Q

Which type of DC motor is best suited for applications requiring excellent torque characteristics and used in dragline excavators?

A

Series-wound motors

176
Q

In which application is a shunt motor most suitable due to the requirement for constant speed and torque maintenance?

A

Production line conveyor systems

177
Q

What advantage do compound motors offer over other types of DC motors?

A

The benefits of both series and shunt motors

178
Q

What is a practical use of direct current generators?

A

Charging batteries

179
Q

What is the main principle of operation for all AC motors?

A

Interaction between magnetic fields

180
Q

What is the primary difference between a synchronous motor and an induction motor?

A

Induction motors operate at a precise speed.

181
Q

How does an induction motor achieve torque and rotation?

A

By creating slip between rotor and stator fields

182
Q

What is the main reason single-phase motors require additional components for starting?

A

The magnetic flux components are equal and opposite.

183
Q

Which type of single-phase motor uses a start winding with a different resistance to create a phase shift?

A

Split-phase induction motor

184
Q

In a capacitor-start motor, what is the purpose of the starting capacitor?

A

To create a phase shift in the circuit

185
Q

Where are shaded-pole motors commonly used due to their low starting torque?

A

Electric fans

186
Q

Which type of motor is used in power tools and household appliances like food blenders?

A

Universal motor

187
Q

How Motor Starters Operate

A

Switching the motor on and off

188
Q

When is a star-delta starter typically used for three-phase motors?

A

When high starting torque is required

189
Q

In which applications are AC generators or alternators commonly used?

A

Hybrid electrical vehicle drives

190
Q

Why are cage induction motors preferred over wound rotor induction motors in many applications?

A

They have no brushes or slip rings.

191
Q

What is the primary advantage of using a star-delta starter for three-phase motors?

A

Soft start to limit mechanical stress

192
Q

Which component provides undervoltage protection in a Direct Online (DOL) starter?

A

Contactor coil

193
Q

Miscellaneous Concepts

A

To control the speed of the motor

194
Q

When is it necessary to switch a motor’s field pole pairs in and out?

A

To achieve synchronous speed

195
Q

What is the primary function of a rotor resistance starter?

A
196
Q

What is the primary function of a rotor resistance starter?

A

To reduce startup currents in the rotor of a wound rotor induction motor.

197
Q

Which type of motor is suitable for a rotor resistance starter?

A

Wound rotor induction motor.

198
Q

How do electronic motor starters achieve a soft start for AC motors during startup?

A

By reducing the motor’s voltage initially and then gradually increasing it.

199
Q

What is the primary advantage of using variable frequency drives (VFDs) with AC induction motors?

A

To save energy and money by adjusting motor speed and torque.

200
Q

Why should measures be taken to prevent continued reversal in motors using reverse-current braking?

A

To ensure safety, as continued reversal can be dangerous.

201
Q

What is the purpose of protective devices like fuses and circuit breakers in electrical circuits?

A

To protect against overcurrent and short circuits.

202
Q

What is the primary function of a relay in an electrical circuit?

A

To mechanically switch a set of contacts based on an electrical signal.

203
Q

How do contactors differ from relays?

A

Contactors are used for switching lower current loads, while relays can handle higher current loads.

204
Q

What is the main purpose of a fuse in an electrical circuit?

A

To protect against overcurrent.

205
Q

How do residual current devices (RCDs) operate?

A

RCDs monitor the current in both line and neutral conductors and trip when an imbalance occurs.

206
Q

Which of the following best describes the main function of a fuse in an electrical circuit?

A

To interrupt the circuit when the current exceeds a safe limit.

207
Q

What is the purpose of a breaking capacity (kA) rating for a fuse?

A

To define the maximum fault current the fuse can safely interrupt.

208
Q

What is the primary difference between miniature circuit breakers (MCBs) and moulded-case circuit breakers (MCCBs)?

A

MCBs are used for final circuits, while MCCBs are used for distribution circuits.

209
Q

How do thermal and magnetic trip mechanisms work in a circuit breaker?

A

Thermal trip responds to overcurrent by bending a bimetallic strip, while magnetic trip responds to short circuits with rapid switching.

210
Q

What is the primary function of an RCD in an electrical circuit?

A

To detect and trip in case of an earth fault.

211
Q

How do RCBOs differ from standalone RCDs?

A

RCBOs combine overcurrent protection with earth fault protection in a single device.

212
Q

What is the primary advantage of using solid-state relays over electromechanical relays?

A

Solid-state relays have no moving parts, increasing reliability.

213
Q

When should rotor resistance starters be used?

A

When dealing with heavy loads.

214
Q

What is the primary function of solenoids in electrical systems?

A

To convert electrical signals into mechanical action

215
Q

Solenoids are commonly used in electromagnetic locking devices for what purpose?

A

To engage the locking mechanism

216
Q

What safety feature is typically associated with solenoids used in locking mechanisms in the event of an electrical circuit failure?

A

Safe drop position

217
Q

When is the term “contactor” more accurately used instead of “relay”?

A

When describing a device that controls both high-current and low-current circuits

218
Q

In the context of motor starters like the direct online (DOL) starter, what role does the contactor play?

A

Operating the start and stop controls

219
Q

What is the primary purpose of BS 3036 rewirable fuses?

A

To act as overcurrent protection devices

220
Q

What factor is applied to BS 3036 fuses due to their lack of reliability in certain conditions?

A

Correction factor (Cf)

221
Q

What is the main advantage of BS 88 fuses with high-rupturing capacity (HRC) or high-breaking capacity (HBC)?

A

They can handle high prospective fault currents

222
Q

What are the three common types of Miniature Circuit Breakers (MCBs) based on their trip characteristics?

A

Type A, Type B, and Type C

223
Q

Which type of MCB is typically used for industrial applications where there are large inrush currents, such as industrial motors and welding equipment?

A

Type D

224
Q

What is the primary purpose of Residual Current Devices (RCDs) in electrical systems?

A

To provide protection against electric shock

225
Q

When are Arc Fault Detection Devices (AFDDs) required to be installed according to BS 7671: 2018 (2022)?

A

In high-risk residential buildings, houses of multiple occupation (HMOs), purpose-built student accommodation, and care homes

226
Q

What is the purpose of the inverse square law in lighting calculations?

A

To calculate the illuminance on a surface at varying distances from a light source

227
Q

What does the cosine law of illumination take into account when calculating illumination on surfaces?

A

The additional area illuminated when light falls obliquely on a surface

228
Q

What is the lumen method used for in lighting design?

A

To find the number of luminaires needed for a specific average illuminance level

229
Q

What best describes the function of a relay in an electrical circuit?

A

Controls one circuit with another circuit

230
Q

In the context of electrical components, what is the primary function of a solenoid valve,

A

Controls the flow of fluids in a system

231
Q

What does the coefficient of utilization (Uf) take into account when designing lighting systems?

A

The reflectivity of room surfaces

232
Q

When designing a lighting system, why is it important to consider the space-height ratio?

A

To determine the number of luminaires required

233
Q

What is the unit of measurement for luminous intensity?

A

Candela (cd)

234
Q

Which type of circuit breaker is suitable for protecting circuits with inductive loads like motors or fluorescent luminaires?

A

Type C MCB

235
Q

In the lumen method, what is used to quantify the efficiency of a lamp or luminaire?

A

Efficacy

236
Q

What is the primary function of Residual Current Circuit Breakers with Overload (RCBOs) in electrical systems?

A

To protect against electrical shock and overloads

237
Q

When are Arc Fault Detection Devices (AFDDs) recommended for installation according to BS 7671: 2018 (2022)?

A

In high-risk residential buildings and care homes

238
Q

Which term describes the total amount of light emitted from a light source?

A

Luminous flux

239
Q

What is the primary purpose of luminaires in lighting systems?

A

To produce light

240
Q

In the context of lighting design, what is the space-height ratio used for?

A

To decide the number of luminaires needed

241
Q

If the space-height ratio (Sr) is 2:1 and the mounting height (H) is 3 meters, what would be the spacing between luminaires (S)?

A

6 meters

242
Q

What does the term “efficacy” describe in lighting systems?

A

The energy efficiency of a lamp in producing light

243
Q

Why is it important to consider the color rendering index (CRI) when selecting luminaires for specific applications?

A

To ensure objects appear in their true colors

244
Q

Which type of lamp is known for producing heat as an unintended byproduct?

A

Incandescent lamp

245
Q

How does convection contribute to heating in convection panel heaters?

A

By circulating warm air

246
Q

Which type of heating system stores heat during off-peak hours and releases it gradually throughout the day?

A

Storage heaters

247
Q

What is the primary function of an immersion heater in a hot water system?

A

To heat the water directly in a vessel

247
Q

What does the efficacy of a lamp indicate?

A

The lamp’s energy efficiency in producing light

248
Q

What is the main purpose of room thermostats in heating systems?

A

To maintain a consistent room temperature

249
Q

How do programmable time controllers enhance heating system efficiency?

A

By reducing energy usage during unoccupied hours

249
Q

What technology allows homeowners to control heating systems remotely through smartphones and voice commands?

A

Home automation

249
Q

Which of the following factors does the space–height ratio (Sr) depend on?

A

Manufacturer’s specifications

250
Q

In what situations is good color rendering particularly important when selecting luminaires?

A

Street lighting

251
Q

Which type of lamp works by passing a current through a filament to produce light?

A

Incandescent lamp

252
Q

What gas is typically added to a tungsten-halogen lamp to prevent filament evaporation?

A

Argon

253
Q

How do radiant heaters primarily heat spaces?

A

By emitting electromagnetic waves

254
Q

Which type of heating system charges up at night when energy is cheaper and releases heat gradually during the day?

A

Storage heaters

255
Q

What is the primary function of a room thermostat in a heating system?

A

To maintain a consistent room temperature

256
Q

What devices is used to adjust heating schedules based on occupancy patterns?

A

Time switch

257
Q

What technology allows homeowners to control heating systems and lighting remotely using voice commands?

A

Wi-Fi

City And Guild Second Edition: for the Level 3 Apprenticeships (5357 and 5393), Level 3 Advanced Technical Diploma (8202), Level 3 Diploma (2365): (6 decks)

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