tailieunhanh - John Wiley And Sons Electronics For Dummies Ebook-Ling P2

Just as you usually use a pound or so of apples to bake your average pie or several tons of steel to build a suburban office park, in electronics, some things just naturally come in small measurements and others in large measurements. That means that you typically see certain combinations of prefixes and units over and over. Here are some common combinations of notations for prefixes and units: Current: pA, nA, mA, µA, A Inductance: nH, mH, µH, H Capacitance: pF, nF, mF, F Voltage: mV, V, kV Resistance: Ω, kΩ, MΩ Frequency: Hz, kHz, MHz, GHz Exploring some new terms Although. | 24 Part I Getting Started in Electronics Just as you usually use a pound or so of apples to bake your average pie or several tons of steel to build a suburban office park in electronics some things just naturally come in small measurements and others in large measurements. That means that you typically see certain combinations of prefixes and units over and over. Here are some common combinations of notations for prefixes and units Current pA nA mA 1A A Inductance nH mH H Capacitance pF nF mF F Voltage mV V kV Resistance Q kQ MQ Frequency Hz kHz MHz GHz Exploring some new terms Although we discussed resistance voltage and current earlier in this chapter some other terms in this section may be new to you. Capacitance is the ability to store a charge in an electric field. This stored charge has the effect of making decreases or increases of voltage more gradual. You can use components called capacitors to provide this property in many circuits. This figure shows the signal that occurs when you decrease voltage from 5 volts to 0 volts both with and without a capacitor. 5 VOLTS O VOLTS WITHOUT CAPACITOR WITH CAPACITOR Frequency is a measurement of how often an AC signal repeats. For example voltage from a wall outlet undergoes one complete cycle 60 times a second. The following figure shows a sine wave. In this figure the signal completes one cycle when the current goes from -5 to 5 volts then back down to -5 volts. If a signal repeats this cycle 60 times a second it has a frequency of 60 hertz. team Line - live informative Nan-cast and Genuine Chapter 1 From Electrons to Electronics 25 5 VOLTS O VOLT - 5 VOLTS 1 CYCLE - 5 TO 5 VOLT AC SINE WAVE Inductance is the ability to store energy in a magnetic field this stored energy resists changes in current just as the stored charge in a capacitor resists changes in voltage. Components called inductors are used to provide this property in circuits. Power is the measure of the amount of work that electric current does .