3.5 Given a scenario, install or replace the appropriate power supply

Question 1

Meaning of PSU?

Answer 1

Power Supply Unit

Question 2

What do PSUs do?

Answer 2

Sends low-voltage DC power to PC components

DC = Direct Current

Question 3

Why do PSUs contain a rectifier?

Answer 3

To convert AC power to DC power

(AC = Alternating Current) (DC = Direct Current)

Question 4

3 components that PSUs comprise of?

Answer 4

• Rectifier
• Transformers
• Filters & regulators

Another important component would be the fan, which dissipates the heat generation

Question 5

Purpose of PSU’s rectifier?

Answer 5

Convert AC power to DC power

Question 6

Purpose of PSU’s transformers?

Answer 6

Lower voltages

Question 7

Purpose of PSU’s regulators?

Answer 7

To ensure consistent output voltage levels

Question 8

2 factors that determines the power supply’s compatiblity?

Answer 8

• Size
• Power connectors

Most PSUs designed for use with desktop PCs are based on the ATX form factor

Question 9

What voltage is typically used in North America?

Answer 9

120 VAC

Question 10

What voltage is typically used in the United Kingdom?

Answer 10

230 VAC

Question 11

What does it mean that most PSUs are dual voltage & auto-switching?

Answer 11

They can adapt to different input voltages automatically

Some PSUs feature a manual voltage switch; fixed types suit either low-line or high-line voltages. Clear voltage compatibility indication is crucial in PSUs and their documentation.

Question 12

What is the range of low-line VAC?

This would be used in regions like North America

Answer 12

100-127 VAC

Question 13

What is the range of high-line VAC?

This would be used in regions like teh United Kingdom

Answer 13

220-240 VAC

Question 14

What is power measured in?

Answer 14

Watts

Question 15

How is Watts calculated?

Answer 15

Voltage multiplied by current (V*I)

Question 16

What power output does a PSU need to power a PC?

Answer 16

Combined power requirements of the PC’s components

Question 17

What is the PSU’s output capability measured in?

Answer 17

Wattage rating

Question 18

What PSU rating is used for standard desktops?

Answer 18

200-300W

Question 19

What PSU rating is used for workstations & servers?

Answer 19

Over 300W

Due to meeting the demands of multiple CPUs, additional memory modules, disk drives, & tape units. Gaming PCs might require 500W or better power supplies to cope with the high specification CPU & graphics card(s)

Question 20

What does PSU efficiency refer to?

Answer 20

How effectively PSU converts grid power to usable PC power

The higher the percentage the better

If a PSU operates at 75% efficiency, it draws more power from the outlet than its output. The extra energy is lost as heat. With rising energy costs and environmental concerns, selecting an efficient PSU is crucial. ENERGY STAR 80 PLUS compliant PSUs must maintain 80% efficiency across load levels.

Question 21

3 voltages that PSUs supply to components?

Answer 21

• 3.3V
• 5
• 12V

Not all components use power at precisely these voltages. Voltage regulators are used to correct the voltage supplied form the PSU to the voltage required by the component.

Question 22

How is a modular PSU unique to other PSUs?

Answer 22

Has detachable power connector cables

Question 23

What systems mainly use redundant power supplies?

Answer 23

Servers

Question 24

What is required to use redundant power supplies?

Answer 24

Compatible motherboard