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Electricity FAQ (frequently asked questions)

Need to write a report about electricity? Want to know more about some aspect of electricity that's caught your interest? Click on the questions below, and you'll be on your way.

1. What is electricity?
2. How is electricity generated?
3. How does electricity travel?
4. How is electricity measured?
5. How many miles of power lines are there in the United States?
6. Do the words "shocked" and "electrocuted" mean the same thing?
7. Why can you sometimes see a spark if you can't see electricity?
8. When a circuit is open, do electrons go backward, or do they just stop?
9. Why does electricity try to get to the ground, and what does it do when it gets there?
10. Why can a bird sit on a power line and not get shocked?
11. What is static electricity?
12. What is lightning?
13. How much energy is in a bolt of lightning?
14. Does lightning ever strike fish?
15. Who holds the world's record for being struck by lightning most often?
16. Why didn't Ben Franklin get electrocuted when he tied a metal key to a kite string and flew the kite in a thunderstorm?
17. Why shouldn't I use a corded phone or electrical appliance during a thunderstorm?
18. How do batteries create electricity?
19. Why don't I get a shock when I touch a battery?
20. What are those little boxes on hair dryer cords?
21. Do electric eels really create electricity?
22. How does a defibrillator work?
23. How does an incandescent light bulb work?
24. How does a compact fluorescent light (CFL) work?
25. How does a light-emitting diode (LED) work?

 

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1. What is electricity?
   Electricity is a form of energy that starts with atoms. Atoms are too small to see, but they make up everything around us. An atom has three tiny parts: protons, neutrons and electrons. The center of the atom has at least one proton and one neutron. At least one electron travels around the center of the atom at great speed. Electricity can be created by forcing electrons to flow from atom to atom.
   
   
   
   
2. How is electricity generated?
   Most electricity used in the United States is produced at power plants. Various energy sources are used to turn turbines. The spinning turbine shafts turn electromagnets that are surrounded by heavy coils of copper wire inside generators. This creates a magnetic field that causes the electrons in the copper wire to move from atom to atom.
   
   
   
   
3. How does electricity travel?
   Electricity leaves the power plant and is sent over high-power transmission lines on tall towers. The strong electric current from a power plant must travel long distances to get where it is needed. Electricity loses some of its strength (voltage) as it travels, so transformers, which boost or "step up" its power, must help it along.
   
   When electricity gets closer to where it will be used, its voltage must be decreased. Different kinds of transformers at utility substations do this job, "stepping down" electricity's power. Electricity then travels on overhead or underground distribution wires to neighborhoods. When the distribution wires reach a home or business, another transformer reduces the electricity down to just the right voltage to be used in appliances, lights and other things that run on electricity.
   
   A cable carries the electricity from the distribution wires to the house through a meter box. The meter measures how much electricity is used. From the meter box, wires run through the walls to outlets and lights. The electricity always is waiting in the wires to be used.
   
   Electricity travels in a circuit. When you switch on an appliance, you complete the circuit. Electricity flows along power lines to the outlet, through the power cord into the appliance, then back through the cord to the outlet and out to the power lines again.
   
   Electricity travels fast (186,000 miles per second). If you traveled that fast, you could travel around the world almost eight times in the time it takes to turn on a light! And if you had a lamp on the moon wired to a switch in your bedroom, it would take only 1.28 seconds after you flipped the switch for electricity to light the lamp 238,857 miles away!
   
   
   
   
4. How is electricity measured?
   Volts, amps and watts measure electricity. Volts measure the "pressure" under which electricity flows. Amps measure the amount of electric current. Watts measure the amount of work done by a certain amount of current at a certain pressure or voltage.
   
   To understand how they are related, think of water in a hose. Turning on the faucet supplies the force, which is like the voltage. The amount of water moving through the hose is like the amperage. You would use lots of water to make it come out really hard (like a lot of watts) to wash off a muddy car. You would use less water flowing more slowly (like less watts) to fill a glass.
   
   watts = amps × volts
   amps = watts ÷ volts
   
   
   
   
5. How many miles of power lines are there in the United States?
   There are more than 500,000 miles of high-voltage transmission lines in the United States and many hundreds of thousands more miles of distribution lines that carry electricity to our homes.
   
   
   
   
6. Do the words "shocked" and "electrocuted" mean the same thing?
   No. People can be shocked by electricity and survive. But when they are electrocuted, it means they have been killed by electricity.
   
   
   
   
7. Why can you sometimes see a spark if you can't see electricity?
   You can't see electricity when it is flowing through a circuit. But if electricity leaves the circuit—like when someone is shocked—you can see a spark. The spark isn't electricity itself. It is a flame that happens when the electricity travels through the air and burns up oxygen particles.
   
   
   
   
8. When a circuit is open, do electrons go backward, or do they just stop?
   Neither. In the wires of an electrical circuit, the electrons are always jiggling around. When a circuit is closed to run an appliance or a light bulb, the electrons jiggle a lot and travel through the wire. When the circuit is open, all the electrons just jiggle where they are—kind of like running in place.
   
   
   
   
9. Why does electricity try to get to the ground, and what does it do when it gets there?
   It's just the nature of electricity to move from an area of higher voltage to an area of lower voltage, if given a path to travel there. The ground is simply the lowest-voltage area around, so if you give electricity a path to the ground, it will take it. When electricity goes into the ground, the ground absorbs its energy.
   
   
   
   
10. Why can a bird sit on a power line and not get shocked?
    It is easier for electricity to keep flowing through the power line than to go through the bird. But if a bird with large wings touches a power line and a tree or power pole at the same time, it provides electricity with a path to the ground, and the bird could be shocked. If a bird touches two wires at once, it creates a circuit—electricity flows through the bird and likely electrocutes it.
    
    
    
    
11. What is static electricity?
    The shock you feel when you touch an object after walking on carpet is static electricity. When you drag your feet across carpet on a dry day, electrons from the carpet get transferred to your body. (Electrons are parts of the atoms that make up all matter.) If you then touch a piece of metal, such as a doorknob, the electrons jump to the metal and you'll feel a shock
    
    
    
    
12. What is lightning?
    Lightning is a large discharge of static electricity. During a thunderstorm, clouds build up a charge when small bits of ice collide through a rising and sinking motion within the clouds. The charges created by these collisions eventually fill up the whole cloud. When there is a big difference in charge between the cloud and its surroundings, the cloud discharges a lightning bolt.
    
    
    
    
13. How much energy is in a lightning bolt?
    One lightning strike carries up to 100 million electrical volts. That's as much electricity as about 8 million car batteries.
    
    
    
    
14. Does lightning ever strike fish?
    Yes, it does. Because water conducts electricity, a lightning strike spreads out along the water's surface. Any fish near the surface of the water get electrocuted.
    
    
    
    
15. Who holds the world's record for being struck by lightning most often?
    According to Guinness World Records, Roy G. Sullivan, a former United States park ranger, was struck by lightning seven times over the course of his 35-year career. Lightning has burned off his eyebrows, seared his shoulder, set his hair on fire, injured his ankle and burned his belly and chest.
    
    
    
    
16. Why didn't Ben Franklin get electrocuted when he tied a metal key to a kite string and flew the kite in a thunderstorm?
    Ben Franklin probably did not do his famous kite experiment the way it is usually portrayed. (Franklin never wrote about it himself, and the only description we have of it was written by another scholar, Joseph Priestley, 15 years later.) Franklin believed lightning was a flow of electricity taking place in nature. He knew of electricity’s dangers, and would probably not have risked being struck by lightning by flying his kite during a storm. It is more likely that Franklin flew his kite before the storm occurred, and that his famous key gave off an electric spark by drawing small electrical charges from the air.
    
    
    
    
17. Why shouldn't I use a corded phone or electrical appliance during a thunderstorm?
    There is a slight chance that a lightning strike could surge through phone lines or through the wires of an electrical appliance. If you were to touch a phone or appliance at just that moment, you could be shocked.
    
    
    
    
18. How do batteries create electricity?
    A chemical reaction within the battery forces electrons to move.
    
    
    
    
19. Why don't I get a shock when I touch a battery?
    There is not enough voltage in a regular household battery to cause a shock. However, car batteries are powerful enough to shock, so you should never tamper with them.
    
    
    
    
20. What are those little boxes on hair dryer cords?
    In the early 1980s, about 18 deaths a year were caused by hair dryers falling into bathtubs or sinks filled with water. Since 1991, hair dryer manufacturers have been required to include GFCIs (ground fault circuit interrupters) on dryer cords. GFCIs cut off electricity to prevent serious shock. Thanks to these devices, the number of hair dryer-related deaths has dropped to an average of two per year.
    
    
    
    
21. Do electric eels really create electricity?
    Yes. An electric eel uses chemicals in its body to manufacture electricity. A large electric eel can produce a charge of up to 650 volts, which is more than five times the shocking power of a household outlet.
    
    
    
    
22. How does a defibrillator work?
    Inside the cells of the heart, tiny electrical currents fire in a steady rhythm. If that rhythm is disrupted due to disease or injury, a heart attack can occur. A defibrillator shocks every cell in the heart at the same time, so they all start up again in rhythm. It's like each cell is dancing to the same beat!
    
    
    
    
23. How does an incandescent light bulb work?
    The wire inside a light bulb is called a filament. It is made of tungsten, a metal that stays solid at high temperatures. Electricity flows through the tungsten filament, causing it to heat and glow. The glow gives off light. Inside a light bulb is a vacuum—in other words, all the air has been removed from inside the glass bulb. (If there were air inside, the wire would burn up.)
    
    
    
    
24. How does a compact fluorescent light (CFL) work?
    Compact fluorescent lights (CFLs) and other fluorescent light bulbs contain gases (argon and mercury vapor) that produce invisible ultraviolet (UV) light when stimulated by electricity. When the UV light hits the white phosphor coating inside the fluorescent bulb, the phosphor illuminates or "fluoresces," changing the UV light into visible light. CFLs are very energy-efficient, using only about one-fifth the energy of a standard incandescent bulb. This is because all of the electricity they use goes toward creating light, whereas the energy used by standard incandescent bulbs creates heat as well as light.
    
    
    
    
25. How does a light-emitting diode (LED) work?
    Like their energy-efficient cousins, CFLs, LEDs don't waste energy on heat so don't get especially hot. But unlike CFLs, LEDs are illuminated solely by the movement of electrons in a semiconductor material. A semiconductor is a material with electrical conductivity (meaning the ability to transfer electrical energy) ranging between that of a conductor and an insulator (hence the prefix "semi"). Inside an LED, when an electrical current passes through the semiconductor material, electrons move through the material and drop to other energy levels, and in the process they emit photons of light. LEDs are becoming an increasingly important and common light source because of their high degree of energy efficiency. We see them particularly in Christmas tree lights and the tubes that light up LED HDTVs.