Books
in black and white
Main menu
Share a book About us Home
Books
Biology Business Chemistry Computers Culture Economics Fiction Games Guide History Management Mathematical Medicine Mental Fitnes Physics Psychology Scince Sport Technics
Ads

Electronics for dummies - McComb G.

McComb G., Boes E. Electronics for dummies - Wiley publishing, 2005. - 433 p.
ISBN: 0-7645-7660-7
Download (direct link): electronicsfordummies2005.pdf
Previous << 1 .. 16 17 18 19 20 21 < 22 > 23 24 25 26 27 28 .. 149 >> Next

Getting a first aid chart
Of course, youíre the safest person on earth, and you will never be electrocuted. But just in case, get one of those emergency first aid charts that
term LinG - live, informative, Non-cost and Genuine !
Chapter 2: Keeping Humans and Gadgets Safe 33
includes information about what to do if anyone else (not you, of course) ever pokes his finger into a wall outlet. You can find these charts on the Internet; try a search for ďfirst aid wall chart.Ē You can also find them in school and industrial supply catalogs.
Helping someone who has been electrocuted may require cardio-pulmonary resuscitation, otherwise known as CPR. Be sure that youíre properly trained before you administer CPR on anyone. Otherwise, you may cause more harm than good. Check out www.redcross.org to get more information about CPR training.
Zaps, Shocks, and Static Discharge
One type of everyday electricity that is dangerous to both people and electronic gizmos is static electricity. They call it static because itís a form of current that remains trapped in some insulating body, even after you remove the power source. With conventional AC and DC current, static electricity disappears when you turn off the power source.
The ancient Egyptians discovered static electricity when they rubbed cat fur against the smooth surface of amber. After they rubbed the materials together, they tended to cling to one another by some unseen force. Similarly, two pieces of cat fur that they rubbed against the amber tended to separate from each other when the Egyptians drew those pieces together. Although the Egyptians didnít understand this mysterious force, they were aware of it. And they had the scratched-up arms to prove it! (Note to Pharaohs: Best not to use live cats for your electricity experiments.)
Carpets don't shock, people do
Carpet shock hasn't killed anyone (that we know of, anyway). The amount of current is usually too low to harm your body. But, because of their extremely small size, the same isn't true for electronic components. Static electricity of just a few thousands volts, a mere tingle to you (because the current is so very, very low), can cause great harm to sensitive electronic components.
As an electronics experimenter, remember to take specific precautions against electrostatic
discharge, or ESD. See the section "Tips for reducing static electricity," later in this chapter, for specific pointers. You can all but eliminate damage from static discharge by taking just a few simple steps to protect yourself, your tools, and your projects from static buildup. The cost for protecting against static electricity is minimal; without knowing it, you may already be on the road to preventing dangerous static buildup in your electronics workshop.
term LinG - live, informative, Non-cost and Genuine !
34
Part I: Getting Started in Electronics
Static electricity hangs around until it dissipates in some way. Most static dissipates slowly over time, but in some cases, it gets released all at once. Lightning is one of the most common forms of static electricity.
Designers make certain common electronic components to hold a static charge, such as the ordinary capacitor (a component that provides the ability to store energy in an electric field). Most capacitors in electronic circuits store a very minute amount of charge for extremely short periods of time. But some capacitors, most notably those used in bulky power supplies, can store near-lethal doses for several minutes or even hours. Use caution when working around capacitors that can store a lot of charge so you donít get an unwanted shock.
That guy from the $100 bill again
Benjamin Franklin, like other scholars of his time, understood quite a bit about static electricity. One of Franklinís many inventions was an early motor that ran completely on static electricity. While Benís motor is little more than a scientific curiosity today, it shows that static is a form of electricity, just like AC or DC electricity.
Imagine a motor without a battery. Ben Franklin had to imagine this because batteries werenít invented until after he died. The honor of inventing the battery in the year 1800 goes to Alessandro Volta ó hence the name of the unit of measure for electromotive force (an attractive force between positive and negative charges), the volt . And even though Franklin didnít come up with the battery, he first coined the term to describe his apparatus that collected static in charged glass plates.
You can encounter static electricity now and then by doing nothing more than walking across a carpeted floor. As you walk, your feet rub against the carpet and your body takes on a static charge. Touch a metal object, such as a doorknob or a metal sink, and the static quickly discharges from your body. You feel that discharge as a slight shock.
How static can turn components to lumps of coal
Electrostatic discharge involves very high voltages at extremely low currents. Combing your hair on a dry day can develop tens of thousands of volts of static electricity, but the current is almost so negligible you seldom notice it. The low current prevents the static discharge from really hurting you when you receive a shock. Instead, you just get an annoying tickle (and maybe a bad hair day).
Previous << 1 .. 16 17 18 19 20 21 < 22 > 23 24 25 26 27 28 .. 149 >> Next