Rectification and fluctuating direct current

Chapter Rectification and fluctuating direct current

Teach Yourself Electricity and Electronics Third Edition Book
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Teach Yourself Electricity and Electronics Third Edition Book

  • maximum, or peak, voltage. In fact, for the common waveshape shown in Fig. 2-8, theeffective value is 0.707 times the peak value. Conversely, the peak value is 1.414 timesthe effective value.Rectification and fluctuating direct current352-8One cycle of utility alternating current. The peak voltage is about165 V.Because the whole cycle repeats itself every1/60 second, the frequency of the util-ity ac wave is said to be 60 Hertz, abbreviated 60 Hz. The word “Hertz” literally trans-lates to “ cycles per second.” In the U.S., this is the standard frequency for ac. In someplaces it is 50 Hz. (Some remote places even use dc, but they are definitely the excep-tion, not the rule.)In radio practice, higher frequencies are common, and you’ll hear about kilohertz(kHz), megahertz (MHz) and gigahertz (GHz). You should know right away the sizeof these units, but in case you’re still not sure about the way the prefixes work, the re-lationships are as follows:1 kHz = 1000 Hz1 MHz = 1000 kHz = 1,000,000 Hz1 GHz1000 MHz = 1,000,000 kHz1,000,000,000 HzUsually, but not always, the waveshapes are of the type shown in Fig. 2-8. This wave-form is known as a sine wave or a sinusoidal waveform.Rectification and fluctuating direct currentBatteries and other sources of direct current (dc) produce a constant voltage. This canbe represented by a straight, horizontal line on a graph of voltage versus time (Fig. 2-9).