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Chapter 3. Electricity and power supplie... > Unit summary: Electricity and power ...

3.4. Unit summary: Electricity and power supplies


Topic A

In this topic, you learned that electricity is the source of energy that powers electronics and appliances. Voltage is the force of electricity. Current is a measure of the flow of electricity. Resistance is a force that opposes current. You also learned about electrical safety and the 1-10-100 rule, which states that you can feel 1 mA, 10 mA makes your muscles contract uncontrollably, and 100 mA can kill you. You learned that static electricity is a buildup and discharge of an electrical charge. You learned how to avoid static by preventing charges from building up and by dissipating charges safely if they do build up. You learned how to open computer cases and follow proper ESD precautions while working inside a computer.


Topic B

In this topic, you learned that power supplies convert wall voltage to the various DC voltages required by the computer's components. To a small extent, the power supplies condition the power signal and bridge very short power outages. You learned about the power demands of various computer components, power supply ratings, and the power connector standards used in modern computers. You also examined power supply form factors. You also learned how to select, replace, and install a power supply.


Topic C

In this topic, you learned about some common symptoms related to power supply failures. You also learned the associated probable causes and suggested solutions to the problems. You learned how to use a multimeter to measure electricity.

3.4.1. Review questions

  1. Which of the following are conductors? [Choose all that apply.]

    A Ceramics

    B Gases

    C Liquids

    D Metals

    E Plastics

  2. Which of the following are insulators? [Choose all that apply.]

    A Ceramics

    B Gases

    C Liquids

    D Metals

    E Plastics

  3. Which of the following is a derived quantity that you can calculate by multiplying the force of electricity caused by a difference in charge at two locations and the measure of the flow of electrons past a given point?

    A Current

    B Electrical power

    C Impedance

    D Resistance

    E Voltage

  4. Which of the following is a force that opposes the flow of DC through a conductor?

    A Current

    B Electrical power

    C Impedance

    D Resistance

    E Voltage

  5. Which of the following is measured in amps?

    A Current

    B Electrical power

    C Impedance

    D Resistance

    E Voltage

  6. Which of the following are measured in ohms? [Choose all that apply.]

    A Current

    B Electrical power

    C Impedance

    D Resistance

    E Voltage

  7. What is the formula relating voltage, current, and resistance?

    A i = V * r

    B r = V * i

    C V = i * r

    D V = i/r

  8. True or false? At a given voltage, current increases as resistance drops.

    True.

  9. True or false? You need to be concerned about electrostatic discharge because it can be fatal to humans.

    False. Electrostatic discharges aren't dangerous to humans, even though the voltage in the system can measure in the range of thousands of volts. However, such discharges are potentially harmful to electronics.

  10. The power requirements of a motherboard are estimated to be which of the following?

    A 5 W

    B 10 W

    C 30 W

    D 50 W

    E 100 W

  11. Which of the following components requires the most power?

    A Adapter card

    B CPU

    C Hard drive

    D Memory

    E Motherboard

  12. More devices draw power at what voltage level than at any of the other ranges?

    A +3.3 V

    B −5 V

    C +5 V

    D −12 V

    E +12 V

  13. Which of the following is a serial ATA power connector?

    A



    B



    C



  14. Which color wire is always connected to ground?

    A Black

    B Green

    C Red

    D Yellow

  15. How many pins does the ATX v2.0 connector have?

    A 16

    B 18

    C 20

    D 24

  16. How many ohms does a multimeter read for a closed circuit, such as a good fuse or good wire?

    Zero


  

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