UNIT REVISION

City & Guilds 2357 Unit 609: Understanding the electricalprinciples associated with the design, building, installation and maintenance of electrical equipment and systems (ELTK08) — Complete Revision Guide

A structured revision walkthrough of every topic in City & Guilds 2357 Unit 609 (Understanding the electricalprinciples associated with the design, building, installation and maintenance of electrical equipment and systems (ELTK08)). Use it as a personal study checklist — work through each topic, tick off the points you can confidently explain or calculate, and use the linked Elec-Mate tools to practice the calculation-led parts. Designed for apprentices working through an NVQ pathway with on-the-job portfolio evidence.

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19 min readUpdated 2026-05-18Andrew Moore, Founder of Elec-Mate

Written and reviewed by Andrew Moore, founder of Elec-Mate, against BS 7671:2018+A4:2026, IET Guidance Note 3 and the IET On-Site Guide.

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Key Takeaways

  • 1City & Guilds 2357 Unit 609 — Understanding the electricalprinciples associated with the design, building, installation and maintenance of electrical equipment and systems (ELTK08) — is a core component of the Level 3 NVQ Diploma in Installing Electrotechnical Systems and Equipment.
  • 2This unit is typically delivered to apprentices working through an NVQ pathway with on-the-job portfolio evidence and covers 12 main topic areas.
  • 3Across the 12 topics there are 47 specific points you should be able to explain, demonstrate or calculate before the end-of-unit assessment.
  • 4Common assessment formats include online multiple-choice exams, written short-answer papers, and practical workshop tasks observed by your tutor.
  • 5Use the structured topic list below as a personal checklist — work through each point and confirm you can explain it without referring to your notes.
  • 6The Elec-Mate apprentice tier includes mock exams, flashcards, and revision notes mapped to this unit. Use the tools to test yourself between college blocks and on-site days.
01 · Unit Revision

Topic 1: Mathematical principles which are appropriate to electrical installation, maintenance and design work

In this section you should be confident with the following points. Each one is a specific topic you should be able to explain, demonstrate, or calculate.

  • Identify and apply appropriate mathematical principles which are relevant to electrotechnical work tasks..
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02 · Unit Revision

Topic 2: Standard units of measurement used in electrical installation, maintenance and design work

In this section you should be confident with the following points. Each one is a specific topic you should be able to explain, demonstrate, or calculate.

  • Identify and use internationally recognised (SI) units of measurement for general variables.
  • Identify and determine values of basic SI units which apply specifically to electrical variables.
  • Identify appropriate electrical instruments for the measurement and calculation of different electrical values..
03 · Unit Revision

Topic 3: Basic mechanics and the relationship between force, work, energy and power

In this section you should be confident with the following points. Each one is a specific topic you should be able to explain, demonstrate, or calculate.

  • Specify what is meant by mass and weight.
  • Explain the principles of basic mechanics as they apply to levers, gears and pulleys.
  • Describe the main principles of the following and their inter-relationships: • force • work • energy (kinetic and potential) • power • efficiency.
  • Calculate values of electrical energy, power and efficiency. 112 City & Guilds Level 3 Diplomas in Electrotechnical Technology (2357) Unit 609 Understanding the electricalprinciples associated with the design, building, installation and maintenance of electrical equipment and systems (ELTK08).
04 · Unit Revision

Topic 4: The relationship between resistance, resistivity, voltage, current and power

In this section you should be confident with the following points. Each one is a specific topic you should be able to explain, demonstrate, or calculate.

  • Describe the basic principles of electron theory.
  • Identify and differentiate between materials which are good conductors and insulators.
  • State the types and properties of different electrical cables.
  • Describe what is meant by resistance and resistivity in relation to electrical circuits.
  • Explain the relationship between current, voltage and resistance in parallel and series D.C. circuits.
  • Calculate the values of current, voltage and resistance in parallel and series D.C. circuits.
  • Calculate values of power in parallel and series D.C. circuits.
  • State what is meant by the term voltage drop in relation to electrical circuits.
  • Describe the chemical and thermal effects of electrical currents. Unit 609 Understanding the electricalprinciples associated with the design, building, installation and maintenance of electrical equipment and systems (ELTK08).
05 · Unit Revision

Topic 5: The fundamental principles which underpin the relationship between magnetism and electricity

In this section you should be confident with the following points. Each one is a specific topic you should be able to explain, demonstrate, or calculate.

  • Describe the magnetic effects of electrical currents in terms of: • production of a magnetic field • force on a current-carrying conductor in a magnetic field • electromagnetism • electromotive force.
  • Describe the basic principles of generating an A.C. supply in terms of: • a single-loop generator • sine-wave • frequency • EMF • magnetic flux.
  • Explain how characteristics of a sine-wave affect the values of A.C. voltage and current..
06 · Unit Revision

Topic 6: Electrical supply and distribution systems

In this section you should be confident with the following points. Each one is a specific topic you should be able to explain, demonstrate, or calculate.

  • Describe how electricity is generated and transmitted for domestic and industrial/commercial consumption.
  • Specify the features and characteristics of a generation and transmission system.
  • Explain how electricity is generated from other sources.
  • Describe the main characteristics of: • single phase electrical supplies • three phase electrical supplies • three phase and neutral supplies • Earth-fault loop path • star and delta connections.
  • Describe the operating principles, applications and limitations of transformers.
  • State the different types of transformer that are used in electrical supply and distribution networks.
  • Determine by calculation and measurement: • primary and secondary voltages • primary and secondary current • kVA rating of a transformer..
07 · Unit Revision

Topic 7: How different electrical properties can effect electrical circuits, systems and equipment

In this section you should be confident with the following points. Each one is a specific topic you should be able to explain, demonstrate, or calculate.

  • Explain the relationship between resistance, inductance, capacitance and impedance.
  • Calculate unknown values of resistance, inductance, inductive reactance, capacitance, capacitive reactance and impedance.
  • Explain the relationship between kW, kVAr, kVA and power factor.
  • Calculate power factor.
  • Explain what is meant by power factor correction and load balancing (neutral current).
  • Specify methods of power factor correction.
  • Determine the neutral current in a three-phase and neutral supply.
  • Calculate values of voltage and current in star and delta connected systems. Unit 609 Understanding the electricalprinciples associated with the design, building, installation and maintenance of electrical equipment and systems (ELTK08).

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08 · Unit Revision

Topic 8: The operating principles and applications of DC machines and AC motors

In this section you should be confident with the following points. Each one is a specific topic you should be able to explain, demonstrate, or calculate.

  • State the basic types, applications and describe the operating principles of DC machines.
  • Describe the operating principles of: • single phase AC motors (capacitor start, induction start, universal) • three phase AC motors (squirrel cage; wound-rotor) • inverter motor/variable frequency drive • synchronous motors.
  • State the basic types, applications and limitations of: • single phase AC motors (capacitor start, induction start, universal) • three phase AC motors (squirrel cage; wound-rotor) • inverter motor/variable frequency drive • synchronous motors.
  • Describe the operating principles, limitations and applications of motor control.
09 · Unit Revision

Topic 9: The operating principles of different electrical components

In this section you should be confident with the following points. Each one is a specific topic you should be able to explain, demonstrate, or calculate.

  • Specify the main types and operating principles of the following electrical components: • contactors • relays • solenoids • over-current protection devices: o Fuses (HRC, cartridge and re-wireable) o Circuit-breakers • RCDs • RCBOs.
  • Describe how the following components are applied in electrical systems/equipment and state their limitations: • contactors • relays • solenoids • over-current protection devices: o Fuses (HRC, cartridge and re-wireable) o Circuit-breakers. • RCDs • RCBOs. Unit 609 Understanding the electricalprinciples associated with the design, building, installation and maintenance of electrical equipment and systems (ELTK08).
10 · Unit Revision

Topic 10: The principles and applications of electrical lighting systems

In this section you should be confident with the following points. Each one is a specific topic you should be able to explain, demonstrate, or calculate.

  • Explain the basic principles of illumination and state the applications of: • inverse square law • cosine law • lumen method.
  • Explain the operating principles, types , limitations and applications of luminaires..
11 · Unit Revision

Topic 11: The principles and applications of electrical heating

In this section you should be confident with the following points. Each one is a specific topic you should be able to explain, demonstrate, or calculate.

  • Explain the basic principles of electrical space heating and electrical water heating.
  • Explain the operating principles, types, limitations and applications of electrical space and water heating appliances and components..
12 · Unit Revision

Topic 12: The types, applications and limitations of electronic components in electrotechnical systems and equipment

In this section you should be confident with the following points. Each one is a specific topic you should be able to explain, demonstrate, or calculate.

  • Describe the function and application of electronic components that are used in electrotechnical systems.
  • State the basic operating principles and applications of electronic components..
13 · Unit Revision

Study This Unit with Elec-Mate

Elec-Mate’s apprentice tier turns this unit checklist into an active study plan. You get mock exam questions, flashcards, and revision notes mapped to this unit, plus working calculators for every calculation-led topic. Most apprentices use the app between college blocks and on the train to site — short bursts of revision compound across the year.

For apprentices

The Elec-Mate apprentice tier includes mock exams, flashcards, and revision notes for City & Guilds 2357 Unit 609 plus every other unit in your qualification. 7-day free trial — see your progress on the tutor dashboard.

A Five-Step Revision Plan for This Unit

A repeatable approach that works for City & Guilds 2357 Unit 609 and every other unit in your qualification.

1

Read through every topic point once

Start at Topic 1 and read every bullet point. Don’t try to memorise — just get familiar with the scope. Note any topic that feels unfamiliar so you can come back to it.

2

Map each topic to its calculator or guide

For calculation-led topics, open the relevant Elec-Mate calculator and try one worked example. For theory-led topics, find the matching section in BS 7671 or the IET On-Site Guide.

3

Work through Elec-Mate mock exam questions

The Elec-Mate apprentice tier includes mock questions mapped to this unit. Aim for 80%+ on a clean run before the real exam.

4

Get hands-on time on the bench

For practical units (inspection and testing, installation), ask your tutor for additional workshop access. The bench is where the points click.

5

Self-explain each topic to a peer

If you can explain a topic in your own words to another apprentice and they understand it, you know it. This is the single highest-leverage revision tactic.

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