Summary

12 IT Essentials: PC Harware and Software Companion GuideThis equation, known as Ohm’s Law, states that voltage is equal to the current multipliedby the resistance.In an electrical system, power (P) is equal to the voltage multiplied by the current, asexpressed by the following equation:P = VIIn an electrical circuit, increasing the current or voltage results in higher power.As an example of how this works, imagine a simple circuit that has a 9-V light bulb hookedup to a 9-V battery. The power output of the light bulb is 100 W. Using the equation to calculatepower, you can calculate how much current in amps would be required to get 100 Wout of this 9-V bulb.To solve this equation, you use the following information that you know:So:P = 100 WV = 9 VI = 100 W / 9 V = 11.11 AWhat happens if a 12-V battery and a 12-V light bulb are used to get 100 W of power?100 W / 12 V = 8.33 ampsThis system produces the same power, but with less current.Computers normally use power supplies ranging from 200 W to 500 W. However, somecomputers may need 500-W to 800-W power supplies. When building a computer, select apower supply with sufficient wattage to power all the components. Obtain the wattage informationfor the components from the manufacturer’s documentation. When deciding on apower supply, be sure to choose a power supply that has more than enough power for thecurrent components.CautionDo not open a power supply. Electronic capacitors located inside a power supply can hold a chargefor extended periods of time.Identify the Names, Purposes, andCharacteristics of Internal ComponentsThis section discusses the names, purposes, and characteristics of a computer’s internalcomponents, as shown in Figure 1-3.