Module 5 Review: Electrical Power

Consolidate Your Learning

A review of the core concepts of electrical power, power supplies, and power protection, with activities to reinforce your understanding.
Author

Chuck Nelson

Published

October 20, 2025

1 Purpose

This document provides a comprehensive review of the key concepts covered in the Electrical Power module. Through a series of active learning exercises and review questions, you will solidify your understanding of everything from basic electrical theory to advanced power protection and troubleshooting. The goal of these activities is to help you connect concepts and apply your knowledge to practical, real-world situations.

2 What You’ll Accomplish

By the end of this review session, you will have:

  • Reinforced your knowledge of voltage, current, resistance, and power.
  • Practiced applying concepts of AC/DC conversion, PSU selection, and power protection.
  • Tested your ability to systematically troubleshoot common power-related issues.

3 Active Learning and Engagement

Complete the following exercises to actively engage with the material and deepen your understanding.

3.1 Exercise 1: Concept Mapping

This activity helps you visually organize the key terms and their relationships, strengthening your mental model of the system.

Using a digital tool like the free online tool draw.io, or another diagramming application, create a concept map that connects the following terms. Draw lines between related concepts and write a short phrase on the line to describe the relationship. Export your finished map as an image and save it for your own review.

  • Voltage (V)
  • Current (I)
  • Resistance (Ω)
  • Ohm’s Law
  • AC Power
  • DC Power
  • Power Supply Unit (PSU)
  • Rectification
  • Filtering
  • Wattage
  • 80 Plus Efficiency
  • UPS (Uninterruptible Power Supply)
  • Surge Protector
  • Pure Sine Wave

Example: You might draw a line from AC Power to PSU and write “is converted by the”.

3.2 Exercise 2: Scenario Challenge

This activity challenges you to apply your knowledge to a realistic problem, a key skill for any IT professional.

Read the following scenario and write your answers to the questions in your personal notes.

A client calls you in a panic. They just finished building their new high-end gaming PC with a top-of-the-line graphics card and a 1000W 80 Plus Gold power supply. The PC was working perfectly for a week. Last night, there was a brief, intense thunderstorm. Today, the PC won’t turn on at all. No lights, no fans, nothing. They mention they had it plugged into a cheap, basic power strip they bought years ago.

  1. Based on the symptoms and the story, what is the most likely point of failure?
  2. What specific electrical event likely caused the damage?
  3. What single piece of equipment could have prevented this issue?
  4. If the client replaces the damaged component and the PC still doesn’t boot, what would be your very first troubleshooting step, following the flowchart from the “Troubleshooting Power Issues” guide?

3.3 Exercise 3: Peer Instruction

This activity helps you solidify your own understanding by explaining concepts to others and hearing their perspectives.

This exercise is for discussion. Find a partner or a small group and choose one of the tabbed sections below. Each person should choose a different topic (A, B, or C) and take a turn explaining it to the others. The goal is to explain it simply enough that someone with no IT background could understand.

Person A explains: The water pipe analogy for Voltage, Current, and Resistance. What does each part of the analogy (water pressure, flow rate, pipe width) represent?

Person B explains: The difference between a basic surge protector and a full Uninterruptible Power Supply (UPS). What can a UPS do that a surge protector cannot?

Person C explains: The safety rule about never opening a Power Supply Unit’s case, even when it is unplugged. What specific components hold a dangerous charge?

Person A explains: The four main stages of AC-to-DC conversion (Transformation, Rectification, Filtering, Regulation) in a linear power supply.

Person B explains: The difference between a Standby (Offline) UPS and a Line-Interactive UPS. Which one is better for handling frequent brownouts and why?

Person C explains: How to properly size a UPS. What is the difference between the VA and Wattage ratings, and which one should you focus on?

Person A explains: The difference between Peak Voltage and RMS Voltage in an AC circuit. Which value do you typically see advertised for wall outlets (e.g., 120V)?

Person B explains: Why a Pure Sine Wave output from a UPS is important for modern computers with Active PFC power supplies. What can happen if you use a cheaper “simulated” sine wave UPS?

Person C explains: The basic steps to test a disconnected PSU using a multimeter. What two pins must be “jumped” to turn the PSU on, and what voltage should you expect on the yellow and red wires?

4 Review Questions

Answer the following questions to test your knowledge.

  1. According to Ohm’s Law, if you have a voltage of 12V and a resistance of 4Ω, what is the current?

    1. 48 Amps
    2. 3 Amps
    3. 0.33 Amps
    4. 16 Amps

  2. What is the primary function of the “Rectification” stage in an AC-to-DC conversion process?

    1. To step down the voltage.
    2. To smooth out the DC pulses.
    3. To convert the AC sine wave into a pulsating DC signal.
    4. To regulate the final output voltage.

  3. Which component is sacrificial in a surge protector and absorbs excess voltage during a spike?

    1. Capacitor
    2. Inductor
    3. Metal Oxide Varistor (MOV)
    4. Transformer

  4. A PSU with an “80 Plus Gold” rating is guaranteed to be at least how efficient at a 50% load?

    1. 80%
    2. 85%
    3. 88%
    4. 90%

  5. You are building a very small, compact Mini-ITX computer. Which PSU form factor would be the most appropriate choice?

    1. ATX
    2. SFX
    3. TFX
    4. 2U Server Module

  6. A user in an area with frequent brownouts (voltage sags) needs a UPS that can correct these issues without constantly switching to its battery. What type of UPS should you recommend?

    1. Standby (Offline) UPS
    2. Line-Interactive UPS
    3. Online (Double-Conversion) UPS
    4. A high-quality surge protector.

  7. When testing a PSU with a multimeter, what DC voltage should you expect to find on the yellow wires?

    1. +3.3V
    2. +5V
    3. +12V
    4. -12V

  8. What is the main advantage of a Switch-Mode Power Supply (SMPS) over an older Linear Power Supply for use in computers?

    1. They are heavier and more durable.
    2. They produce less electrical noise.
    3. They are significantly more efficient and compact.
    4. They do not require a transformer.

  9. A computer and monitor have a combined maximum power draw of 350 Watts. You want to buy a UPS with a 25% safety margin. What is the minimum Wattage rating you should look for in a UPS?

    1. 350W
    2. 400W
    3. 438W
    4. 500W

  10. To safely test a disconnected ATX PSU, you need to jump-start it. This involves connecting the PS_ON pin to which other pin on the 24-pin connector?

    1. Any red wire (+5V)
    2. Any yellow wire (+12V)
    3. Any black wire (Ground)
    4. The purple wire (+5VSB)
    1. 3 Amps
    1. To convert the AC sine wave into a pulsating DC signal.
    1. Metal Oxide Varistor (MOV)
    1. 90%
    1. SFX
    1. Line-Interactive UPS
    1. +12V
    1. They are significantly more efficient and compact.
    1. 438W
    1. Any black wire (Ground)

5 Reflect and Review

ImportantFinal Reflection: 3-2-1

You’ve reached the end of the module review. Take a final moment to synthesize your thoughts. In your personal notes, write down:

  • 3 concepts from this module that you feel most confident about now.
  • 2 topics that you found most interesting or surprising.
  • 1 area you still want to review or a question you plan to ask.
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