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Professor Quester Answers
Questions on Electricity



Dear Dr. Quester:
In chemistry, We have a science lab to make a battery strong enough to light a small flashlight light bulb. We know the copper and zinc are the best metals to use but we dont know what kinda acid to use. We've tried mixing all the acids together and hooking them up all together, but it doesn't work. We have as high as 1 volt but no currency flow. We are desperate! We tried cheating by sticking a battery in a lemon to hide it, but the teacher asked me what was in the lemon. My question is how can I light this tiny bulb light???? HELP????   (Connie, 11th grade, Seattle, WA.)

The Professor Answers:
A lemon will create a small amount of electricity, but only about 0.75 volt...not enough to light a flashlight bulb. See our science project page on how to make a lemon battery.

What you probably should be making is a very simple battery called a Voltaic Pile. It is named after Count Alessandro Volta, an Italian scientist who made the first battery in the about 1800. He made a "sandwich" of paper soaked in salt water between a piece of silver and a piece of zinc and stacked those sandwiches together. Here's how you can do it.... but you'll need some help from an adult.

What you need:
  1. An empty aluminum can
  2. Four pennies
  3. Two pieces of wire (it should be fairly thin wire)
  4. Paper towels soaked in salty water
  5. Some tape
  6. Pair of scissors
What to do:
  1. Take the aluminum can and cut four round pieces of aluminum out of the side of the can, about the same size as a penny.
  2. Sandwich a piece of wet, salty paper towel between a penny and a piece of aluminum from the can.
  3. Tape the bare end of a wire to the penny.
  4. Make thee more sandwiches of penny, salty paper towel and aluminum.
  5. Stack the sandwiches together so the aluminum on the bottom of one "sandwich" rests on tope of the penny on the top of the next "sandwich." Make a stack of all the pieces.
  6. Tape the bare end of the other piece of wire to piece of aluminum on the bottom of your Voltaic pile.
  7. Now take the free end of each wire and touch both ends lightly to your tongue. You will feel a slight tingle of electricity but it won't hurt you. How they should stack up with no spaces, everything touching.
    
                 ______________________________ wire
                /
               /
           [PENNY]
         ____________  towel
          {ALUMINUM}
           [PENNY]
         ____________  towel
          {ALUMINUM}
           [PENNY]
         ____________  towel
          {ALUMINUM}
           [PENNY]
         ____________  towel
          {ALUMINUM}
                \
                 \_____________________________ wire
    
    
    How it works:

    In your Voltaic pile, chemical reactions between the aluminum, copper in the penny and the salty water in the paper towels cause a tiny electric current. The current flows from one wire through your tounge and into the other wire, completing the circuit at the bottom of the Voltaic pile.

    Now, attach one wire to the center bottom of the light bulb and another wire to the side of the metal base of the bulb. Don't let the wire that attaches to the very bottom touch the metal side of the bulb.

                  *attach one wire here at the very bottom of the base
           _/_\_
          <     >    
          <     >      light bulb screw-in base
          <     >    
          <     > *attach the other wire here to the metal side
          / light\
         /  bulb  \
        /          \
        |          |
        |          |
        (          )
        ( _________)
    
    Keep stacking the pennies until you get a current strong enough to light the bulb. That should work....but I haven't tried it.

    Hope your experiment and project works. Good luck!!!




    Dear Professor Quester:
    My son who is 13 years old is trying to gather information on fluorescent lighting. Can you help him out? He needs to know:
    1. How it works
    2. Who invented it
    3. Projects he can do as a class science project
    Thank you for your help.   (Jeannie, Monterey, California)

    The Professor Answers:
    As your son is already aware, incandescent bulbs work because a filament (thin wire with a high melting point) is heated by an electric current until the filament glows, emitting light and lots of heat. The fluorescent lamp is another type of electric-lighting bulb but works differently.

    A fluorescent bulb or lamp (as they are called in the industry) is a glass tube coated on the inside wall with a fluorescent material known as phosphor. The tube is filled with a gas and a small amount of mercury (in a liquid form) and is sealed. When a suitably high voltage (electric current) is applied between the electrodes at each end of the tube, the gas ionizes resulting in an electric current flowing through the tube (ionization is simply a group of atoms or molecules that have an electric charge). This also vaporizes the mercury. The current excites the vaporized mercury which returns back to liquid by the emission of ultra-violet (UV) radiation. Most of UV radiation is invisible but a funny thing happens when the UV radiation reaches the tube walls. The phosphor coating absorbs the UV, become excited (actually that is a scientific term) and re-emits it as visible light. It is the type of phosphor or coating that makes the fluorescent light either bright white, soft yellow or pink, depending on the type of light that is preferred.

    The major difference between incandescent and fluorescent bulbs is energy efficiency. A 40-watt fluorescent lamp produces as much light as a 150-watt incandescent bulb. Even though the purchase price is higher, over its useful life, an 18-watt fluorescent light bulb saves 80 pounds of coal used to produce electricity. This means 250 pounds less of carbon dioxide released into the Earth's atmosphere. Because of this efficiency, fluorescent lamps produce less heat than incandescent bulbs. Fluorescent lamp technology has made significant advances over the past few years. Now there are new compact fluorescent lamps that can be used in regular home light fixtures.

    The inventor of the fluorescent lamp... It seems to be a group effort in the labs however Albert Hall, in 1927, made improvements to the lamps so many consider him the "modern" inventor. The fluorescent lamps were introduced into the marketplace in 1938.

    Regarding science projects...it would be up to your son to decide what he would like to do. It could be as simple as comparing energy uses between incandescent bulbs and fluorescent (as well as halogens, and other types of bulbs); doing a plant-growing experiment using fluorescents, natural daylighting, and other types of bulbs; experimenting why the same colors appear different in direct light, incandescent and fluorescent light...

    Some other web sites you might look at are:

    San Diego Earth Times High-efficiency Fluorescent Lighting Cost Savings Calculator
    and
    How Things Work, by Louis A. Bloomfield

    Good luck!




    Dear Dr. Quester:
    What does a parallel bulb circuit look like? What Does a series bulb circuit look like? What does a parallel cell circuit look like? What does a series cell circuit look like?   (Amanda, 6th grade, Chambersburg, Penn.)

    The Professor Answers:
    I can't show you what a series or parallel circuit look like but I can explain what they are. To see a picture of these types of circuits, I'd suggest you check out any science book and look under circuits.

    There are two different ways of wiring bulbs into a circuit (a circuit is a fancy word for a loop of wire). One way is to wire all the bulbs on the same wire, starting from the positive battery end point then linking each bulb together and ending on the negative battery end. This is called a series circuit, everything is on one wire or circuit. A series circuit looks like a big loop or a group of people holding hands in a circle facing towards the center of the circle. The bulbs in a series circuit give out only a dim light because they are all sharing the same power. If you take out one bulb, it breaks the circuit and the other bulbs go out as well.

    The second way of wiring is to give each bulb a separate circuit. These are called parallel circuits. Let's take the same bulbs and wire them so each bulb has two wires connecting them from the battery ends. Once again, think about a group of people. This time, imagine them, instead of holding hands facing the center, they're in a line facing the next person's back. Their hands are straight out and each hand is holding on to a rope (or wire). The battery is at the beginning of the line with one wire connected to the positive terminal and one to the negative. Instead of a single wire, there are two. These bulbs in a parallel circuit will look almost as bright as just one bulb in a series circuit. If you take out one bulb, all the other bulbs will stay on.

    I've never heard of a series or parallel cell circuits unless you are referring to a battery cell.

    Hope this helps.




    Dear Dr. Q:
    Is it better to turn computers off in a class room environment if they are going to be used again within a couple of hours? Since these have energy efficient monitors, it seems harder on the systems to keep turning them off and on. Thanks for any help.

    The Professor Answers:
    Computers should be turned off over night, but between classes...even for a couple of hours it's probably better to leave them on. It's not so much a matter of energy consumption as it is MTBF -- mean time between failures -- the rate that the on-off switch is going to break. Spinning down and up a hard drive could also cause problems for the drive or for data that is being written to the drive as it is turned off. So, you are protecting the equipment by leaving the computers on during the day.

    A CPU draws less than a couple hundred watts per hour. So, even 20 computers is only going to be 4 kilowatts, about 40 worth of electricity per hour, at 10 per kWh.

    Some CPUs have an energy-saver cycle that spins down the hard drive and other functions, keeping the machines in a stand-by mode when not used for a set period of time. These Energy Star-labelled machine should have a setting in the computer's control panel to set that sleep mode.

    I would recommend, however, if it's going to be longer than a couple of hours to turn off the machines....but if it's just between classes...leave them on. We normally leave our machines on here all day...even if we're going to lunch or attending a meeting for an hour or so. We turn them off at night.

    There is a caveat....some computers, like servers, may have to be left on all the time.

    Hope that helps! It may make a good class assignment to check to see how much the energy the computers are actually using.




    Dear Professor Quester:
    We have a couple of questions to stump you:

    1. What experiment was Millikan known for?
    2. a) The Flame Test

      b) Oil drop

      c) The Gold Foil Test

      d) Burning pigs to figure the mole-mass ratio

    3. Why is energy important to us?
    (Katie P. & Kelly B., Forest Hills Central, Grand Rapids, Mi)

    The Professor Answers:
    Pretty heavy-duty questions. Well, here goes.

    I suppose that you're referring to Robert Andrew Millikan, a US physicist, who won the Nobel Prize in 1923 for his work on the elementary charge of electricity and on the photoelectric effect. Dr. Millikan first performed the "oil drop test" in 1909 making it the first direct and compelling measurement of the electric charge of a single electron. In other words, he figured out a straightforward method of measuring the very small electric charge that is present on many of the droplets in an oil mist. But you must know that since you asked me the question although I liked your burning pigs answer.

    Now regarding why energy is important to us. There are lots of answers to that question. The obvious answer is that we need energy in the form of electricity (and you know what we use that for) and to drive vehicles and heat and cool our homes and schools. However, people got along without electricity and cars and TV and central heating and cooling for thousands of years before today. I think the more important reason we need energy is that we eat food grown by the sun (the life energy force) to fuel our bodies, producing energy so that we can walk, run, think and live. Without the sun and all the things that it provides, we would be non-existent. Why do you think energy is important?




    Dear Professor Quester:
    Why is it so important to turn off the lights when you leave the room? My sister makes a big deal everytime I forget.   (Rob S., Papago Elementary School, Phoenix, AZ)

    The Professor Answers:
    Actually, your sister is one smart person. She knows that leaving lights on when you don't need them is bogus and a total waste. It uses electricity, and then power companies have to build extra power plants to produce that extra electricity. That can cause more smog and more dirty air and more global warming and other "unfriendly-to-the-environment" things. Yuck!

    Another thing. Wasting energy wastes money. Just one 100 watt incandescent light bulb burning for an hour uses a penny's worth of electricity. Now, a penny may not seem like much until you multiply it by all the lights around the house and all the hours that you forget to turn them off. Even leaving the TV on when nobody's watching can waste up to 6 cents an hour. Add all that up each month and it's enough to buy yourself something you've been bugging your parents for or maybe a nice present for your way-cool sister, who you should listen to more often.

    Thanks for asking!




    Dear Professor Quester:
    What is electricity?  (Connie B., Age 11, Orangevale, California)

    The Professor Answers:
    Electricity is a kind of natural energy caused by the flow of tiny parts of atoms called electrons. All matter is made up of atoms, and all atoms have electrons in them. Some kinds of atoms have electrons that are loosely attached, and they can easily be made to move from one atom to another.

    When electrons move among the atoms of matter, a current of electricity is created. This electric flow or "current" lights lamps and runs TV sets and many other appliances.




    Dear Professor Quester:
    How do batteries work?  (Johnathan T., Age 9, Sacred Heart School, Sacramento, California)

    The Professor Answers:
    A battery produces and stores up electrical energy. Electric current is generated when chemicals react with each other.

    A flashlight battery is a good example. Inside a little can made of zinc is a carbon rod. Ammonium chloride (uh-MOE-nee-um KLOHR-ide) paste fills up the can. The ammonium chloride causes the carbon and zinc to react. Their electrons start moving around. When this happens, an electric current is produced. It flows between the carbon and the zinc.

    A car battery uses two kinds of chemicals -- lead and lead peroxide (instead of carbon and zinc). These chemicals are in the form of solid plates. There is a sulfuric (sull- FYOOR-ick) acid mixture around the plates. The acid makes the plate materials react. While your car is running, it has a small device called a generator that recharges the battery so it can be used the next time you start up.

    When all the chemical energy from the plates has changed to electric current, the battery is dead. Then an external battery charger can be used to reverse the chemical reaction and put more energy back into the battery. So, unlike a flashlight battery, which cannot be recharged, this battery can once again store up chemical energy. Now it can start the engine and run the lights again.

    You might consider changing your flashlights' and toys' batteries to ones that can be recharged. That way you won't have to throw away old batteries and buy new ones. A rechargeable battery can be used again and again. This helps save energy, too!



    If YOU have a question about energy, send your question by e-mail to "Professor Quester."
    Ask your parents or teacher first before sending an e-mail. Please tell us your grade level, the name of your school and your city. We will usually respond within four or five days.


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