Computer Power

Question 1

What is the most important safety rule before working inside a computer?

Answer 1

Always disconnect from the power source first — risk of electrocution exists from direct power and from capacitors inside components that may still store charge

Question 2

Why should you never connect yourself to a building’s ground wire?

Answer 2

A building’s ground wire can become energized at any time creating a serious electrocution risk

Question 3

What does a power supply do inside a computer?

Answer 3

It converts AC (Alternating Current) from the wall outlet into DC (Direct Current) that the motherboard and internal components require

Question 4

What AC voltages is a typical power supply designed to accept?

Answer 4

120V AC or 240V AC depending on the region

Question 5

What DC voltages does a power supply output?

Answer 5

3.3 volts, 5 volts and 12 volts — and in some cases negative 12 volts and negative 5 volts for legacy components

Question 6

What is an ampere (amp)?

Answer 6

A measurement of the number of electrons moving past a single point in one second — think of it as the volume of water flowing through a hose

Question 7

What is voltage?

Answer 7

The pressure of electricity on a wire — similar to water pressure in a hose; increasing voltage increases electrical pressure

Question 8

What is wattage and how is it calculated?

Answer 8

Wattage is a measurement of real power use — calculated by multiplying volts by amps (Watts = Volts x Amps)

Question 9

What is the wattage of a device using 120V and 0.5 amps?

Answer 9

60 watts (120V x 0.5A = 60W)

Question 10

What is Alternating Current (AC)?

Answer 10

Current that constantly reverses direction — delivered by power plants to wall outlets and represented visually as a wave

Question 11

What are the AC power standards for the US/Canada vs Europe?

Answer 11

US/Canada — 110 to 120V AC at 60Hz; Europe — 220 to 240V AC at 50Hz

Question 12

What is Direct Current (DC)?

Answer 12

Power that moves in a single direction with a constant voltage — represented visually as a straight line with dashes beneath it

Question 13

What is the risk of plugging a power supply set to 120V into a 230V outlet?

Answer 13

The power supply will be overloaded and will likely fail catastrophically

Question 14

What do most modern power supplies do differently from older ones regarding voltage switching?

Answer 14

Modern power supplies auto-detect input voltage and adjust automatically; older ones required a manual switch to be set to 120V or 230V

Question 15

What is the main power connector on a motherboard and what voltages does it carry?

Answer 15

A 24-pin connector providing 3.3V, 5V and 12V DC — originally 20-pin; a 24-pin connector is backwards compatible with 20-pin boards

Question 16

What is +5V SB and what is it used for?

Answer 16

Standby power — provides power to the motherboard while in sleep or standby state so it can be woken via network signal or front panel button

Question 17

What is +12V DC power primarily used for?

Answer 17

Powering PCIe adapters, hard drives and other components requiring higher voltage

Question 18

What is +3.3V DC power primarily used for?

Answer 18

Powering the motherboard, M.2 slots, RAM and other onboard components on modern motherboards

Question 19

What is -12V DC power used for?

Answer 19

Integrated network (LAN) connections on the motherboard and some older PCI cards

Question 20

What are redundant power supplies and where are they used?

Answer 20

Two power supplies each capable of supporting 100% of system power needs — used in servers and infrastructure to maintain uptime if one fails

Question 21

What does hot swappable mean in the context of server power supplies?

Answer 21

The power supply can be removed and replaced while the system is still running without causing downtime

Question 22

What is the difference between a fixed and a modular power supply?

Answer 22

A fixed power supply has all cables permanently attached; a modular power supply allows you to connect only the cables you need reducing case clutter

Question 23

What is a good rule of thumb when calculating the wattage needed for a power supply?

Answer 23

Choose a power supply where your actual load is no more than 50% of its rated wattage — leaving headroom for growth and reducing strain

Question 24

What is the 80 Plus certification for power supplies?

Answer 24

A certification indicating at least 80% efficiency during AC to DC conversion — tiers from lowest to highest are 80 Plus, Bronze, Silver, Gold, Platinum and Titanium

Question 25

What happens to the power lost during AC to DC conversion?

Answer 25

It is converted to heat — less efficient power supplies generate more heat creating additional cooling demands

Question 26

What is the typical efficiency range for power supplies?

Answer 26

Between 80% and 96% depending on quality and certification tier

Question 27

Does a higher wattage power supply make a computer faster?

Answer 27

No — wattage only affects how much power is available to components; it does not increase processing speed

Question 28

Does increasing the wattage rating of a power supply change its physical size?

Answer 28

No — the physical size of a standard power supply remains the same regardless of wattage rating

Question 29

True or False: It is safe to work inside a computer as long as it is switched off but still plugged in.

Answer 29

False — you must disconnect from the power source entirely; capacitors can still hold charge even when the system is off

Question 30

True or False: A building's ground wire is always safe to connect to for grounding purposes.

Answer 30

False — a building's ground wire can become energized at any time and must never be connected to a person

Question 31

True or False: Computer motherboards run on AC power.

Answer 31

False — motherboards and internal components require DC power; the power supply converts AC from the wall to DC

Question 32

True or False: Watts = Volts x Amps.

Answer 32

True

Question 33

True or False: The US uses 220-240V AC at 50Hz.

Answer 33

False — the US uses 110-120V AC at 60Hz; Europe uses 220-240V AC at 50Hz

Question 34

True or False: Plugging a power supply set to 120V into a 230V outlet will simply reduce performance.

Answer 34

False — it will likely cause a catastrophic failure of the power supply

Question 35

True or False: A 24-pin ATX power connector can be used on an older 20-pin motherboard.

Answer 35

True — the last four pins simply go unused

Question 36

True or False: Redundant server power supplies each only handle 50% of the load and cannot support the full load alone.

Answer 36

False — each supply is designed to handle 100% of the load independently; under normal operation they share the load at 50% each

Question 37

True or False: A modular power supply comes with all cables permanently attached.

Answer 37

False — a modular power supply allows you to connect only the cables you need

Question 38

True or False: An 80 Plus Titanium rated power supply is more efficient than an 80 Plus Gold rated supply.

Answer 38

True — Titanium is the highest efficiency tier in the 80 Plus certification program

Question 39

True or False: A higher wattage power supply will make your computer run faster.

Answer 39

False — wattage only affects available power capacity not processing speed

Question 40

True or False: The physical size of a power supply changes as its wattage rating increases.

Answer 40

False — the physical form factor remains the same regardless of wattage rating

Question 41

True or False: The +5V SB rail is only active when the computer is fully powered on.

Answer 41

False — +5V SB provides standby power when the system is sleeping or off so it can be woken remotely or by button press

Question 42

Scenario: A technician is about to open a desktop computer. What must they do before touching anything inside?

Answer 42

Disconnect the computer from the power source entirely — to avoid electrocution from the supply and to allow any capacitors to discharge

Question 43

Scenario: A user moves their computer from the US to Germany. The manual voltage switch is set to 120V. What could happen?

Answer 43

The power supply will be overloaded by the 230V European outlet and will likely fail catastrophically — the switch must be changed to 230V first

Question 44

Scenario: A device runs at 120V and draws 2 amps. What is the wattage?

Answer 44

240 watts (120V x 2A = 240W)

Question 45

Scenario: A server administrator needs to replace a failed power supply on a live production server without downtime. What feature makes this possible?

Answer 45

Hot swappable redundant power supplies — the second supply takes full load while the failed one is replaced

Question 46

Scenario: All components in a new PC require a maximum of 400 watts. What wattage power supply should be purchased?

Answer 46

At least 800 watts — following the rule of thumb to run at no more than 50% of the power supply's rated capacity for headroom and longevity

Question 47

Scenario: A technician wants to minimize cable clutter inside a high-end build. What type of power supply should they choose?

Answer 47

A fully modular power supply — only needed cables are connected keeping the interior tidy and airflow unobstructed

Question 48

Scenario: A company wants to reduce electricity costs and heat output. What power supply specification should they prioritize?

Answer 48

A high 80 Plus efficiency rating such as Gold, Platinum or Titanium — more efficient conversion means less heat and lower electricity bills

Question 49

Scenario: A technician tests an outlet and reads 230V AC at 50Hz. Where is this system likely located?

Answer 49

In Europe — 230V AC at 50Hz is the European standard

Question 50

Scenario: A fixed power supply has several unused cables bunched up inside the case. What is a better alternative?

Answer 50

A modular power supply — unused cables can be removed entirely keeping the case cleaner and improving airflow