PC Hardware

Lesson Summary : Supplying Power to a Computer

The following points summarize the main elements of this lesson:

  • Power-supply problems can be caused by component failures within the power supply or from the power source.

  • Two devices protect against external power problems-surge suppressors and UPSs.

Tutorial Summary

The following points summarize the key concepts in this tutorial:

Power Supplies

  • The key to specifying the proper size of a power supply for a computer is to add together the power requirements for all the components. It is important to be sure to add extra power to allow for boot up.

  • Electrical power is measured in watts.

  • Proper installation of the P8 and P9 connectors is important to prevent damage to the motherboard. The black (ground) wires must be installed side by side.

  • Molex and mini connectors are used to connect power to devices such as floppy disk and hard disk drives.

Power-Supply Problems

  • The flow of power into a computer must be managed in order to prevent damage and/or loss of data.

  • Surge suppressors will eliminate some higher-than-normal voltage problems.

  • High-quality UPS devices will eliminate most power fluctuations caused by too much or too little voltage.

  • Check power supplies when there are unusual problems with memory and PC operations that do not quickly point to another cause.


  1. Explain the difference between spikes, surges, and sags.

  2. What are the two types of power-supply connectors to the motherboard?

  3. What are the two types of power-supply connectors to devices such as drives?

  4. Name two benefits of having a UPS on a system.

  5. Describe the difference between a brownout and a blackout.

  6. When you purchase a UPS, what is the most important thing to consider?

  7. Will all surge suppressors provide protection against lightning strikes?

  8. What is the best defense against spikes caused by lightning?

  9. What is the most important thing to remember when connecting a P8 and P9 connector to a motherboard?

  10. Explain the difference between the mini connector and the Molex connector.

  11. Describe the best way to make sure a new power supply matches the one you are replacing.

  12. What is the primary use of mini connectors?

  13. A computer power supply has both 5-volt and 12-volt outputs. The 5-volt output is used to power _____________, and the 12-volt output is used to power _____________.