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Science Research Experiments for Young People
By George Barr, John Teppich
Dover Publications, Inc.Copyright © 1989 Dover Publications, Inc.
All rights reserved.
Making sure about things
Before you start your first experiment it is a good idea to consider what you have to do to get accurate results.
Always state your problem so clearly that you know exactly what you are looking for. Plan carefully, get good advice, and learn facts and techniques you may need for the experiment. If possible, work with an interested partner.
One of the best ways to make certain that everything is correct is to repeat the experiment many times. Test your results in every way. Think of possible sources of error. Invite your friends' criticism. Also, see if you get the same answers when you attack the problem in an entirely different way.
Always gather as much evidence as you can before you draw your final conclusions. It is unscientific to be satisfied with only one experiment.
Another important part of research work is to be able to make accurate comparisons before and after experimentation. Wherever possible you should have another setup just like the one on which you are working. All the conditions for both must be exactly the same except for the one thing that you are doing differently to the experimental one.
In this way you can compare one thing at a time and not have to guess about the reason for any change. This kind of duplicate setup is called a control, and it is used in many experiments in this book.
For example, suppose you used a fertilizer on several plants and the plants grew very large. Could you honestly say that the fertilizer did it? Someone might say that the plants would have grown large without the fertilizer. But if you had several similar plants under the same conditions which did not receive the fertilizer you would have a better basis for comparison. The unfertilized plants are called controls.
ELECTRICITY AND MAGNETISM
Does your steam radiator have a north and a south pole?
Bring a magnetic compass close to the top of a radiator in your home. You will probably find that the north end of the compass needle points to it
Place the compass at the lower end of the radiator and the north end of the needle will swing away.
This shows that the radiator has two different poles and is therefore a magnet.
If you go through the house testing different iron objects you will become more and more excited at the number of weak magnets you have around you.
You have probably learned that iron objects become magnetized when they are near magnets. In this case, the earth is the magnet.
You will find that in order for these iron objects to have different poles on the top and bottom they must have been in one position for some time. In this way the iron in them is lined up in the earth's magnetic field.
You can devise many experiments that may occur to you. For example, a tin can of food from the pantry shows a north and south pole because it is about 98 per cent steel and has been in a vertical position for some time.
Turn the can over and test it daily. How long before it loses or changes its poles? Does a larger can take longer to change than a shorter one? If a can shows no poles, how long will it take for it to do so?
Here are some iron objects that may have north and south poles:
radiators sinks (porcelain over iron)
floor lamps bathtubs (porcelain over iron)
umbrellas in stands wastepaper baskets
stoves plates behind doorknobs
metal table legs gates and fences
alarm clocks vertical steel columns in basemen
hinges on doorst
electric switch plates TV cabinets
How strong is your electromagnet?
You probably know how to make an electromagnet. Simply wind insulated wire around a nail. When the ends of the wire are connected to a source of electricity the nail will behave like a magnet.
You can test its strength by counting how many small nails it can pick up.
You will find that the more turns there are and the more electricity you use, the stronger the electromagnet will become.
However, your research problem is to find out whether an electromagnet becomes twice as strong when it has twice as many turns.
You will also learn whether the electromagnet is twice as strong when the source of electricity is doubled.
Use 18-gauge bell wire and make the turns around a 4-inch spike, starting at the head. Use the large (Number 6) dry cells.
Copy the chart on page 16 into your research notebook.
Complete it and study the findings.
Have you found that at a certain point the electromagnet stops getting stronger? Beyond that point the increase in strength does not keep in step with the number of turns of wire or the amount of electricity supplied to the wire.
You must remember, too, that the more turns you make, the less current will go through the wire.
Watts in the house
It is useful to know how many watts an electrical device uses, because then you can find the cost of operating it. You can also learn whether a circuit is being overloaded and is in danger of "blowing" a fuse.
Most pieces of electrical equipment have manufacturers' plates on them that give the wattage. However, if this plate is not present you can use the regular electric meter to help you find the information. This meter is usually in the basement or outside the building.
In addition to the clocklike dials in the meter, there is a spinning disk that is pivoted between the poles of magnets. It goes around and around when electricity is being used in the house.
This circular aluminum disk has a black spot painted on its edge so you can tell when it makes one revolution.
The more electricity you use, the faster this disk turns. But what is more interesting is that the speed corresponds to the number of watts used. In other words, it will spin five times as fast for 500 watts as for 100 watts.
To start the test, see that no electrical device is operating in your house. If the refrigerator, oil burner, or air conditioner starts up while you are making a reading, disregard your results and wait until it goes off. Perhaps your parents will not mind shutting them off for a very short time.
Since electric clocks use only 2 watts, they will hardly affect your figures unless you have several in the house.
Now place a 100-watt bulb in a socket and note how many seconds it takes for the black spot to come around five times. Remove the 100-watt bulb and plug the device with the unknown wattage into any outlet in the house. Again, count the seconds for five turns.
If the unknown device makes the disk turn twice as fast as before, then it is using two times as much electricity. It is therefore a 200-watt appliance.
If the disk turns twenty times as fast as it did for the 100-watt bulb, it is consuming twenty times as much electricity, or 2,000 watts.
On the other hand, if the disk turns half as fast as for the 100-watt bulb, then you have a 50-watt device.
By estimation you can get fairly accurate results.
It is a good idea to work with a friend who does the timing while you watch the turning.
Use a flashlight when you are in the basement. This is not a dangerous experiment, but just to be on the safe side, make sure all the fuse boxes are closed. Do not touch anything near the meter box.
By the way, do all the 100-watt bulbs you have in the house make the disk turn at the same rate? Try testing them. The results may surprise you.
Make a chart in your research notebook like the one shown on page 20.
Fill in the number of seconds needed for five turns of the disk when each device is plugged in separately.
Figure out the wattage.
Compare this with the wattage printed on the device.
More to find out:
How much electricity is used in your house?
It is easy to read the electric meter. It has four dials. To read it, start with the left dial. Write down the number that the indicator passed last. Do the same for the other three dials. The number of kilowatt-hours is the number obtained when all four figures are written together. For example, the dials may read 6705. If next week the new reading is 6805, then 100 kilowatt-hours have been consumed. Make graphs showing how much is used daily for a week.
Is the north pole of a magnet as strong as the south pole?
Devise an accurate and convincing test. HINT: See how many tacks are picked up by each end.
Can you magnetize recording tape?
If you own or can borrow a tape recorder you can do some experiments. The plastic recording tape contains iron particles which can be arranged in certain positions in the tape during the recording process. Try to pick up recording tape with a magnet. You might also try to magnetize a 1-inch separate piece of tape by rubbing one end of it with one end of a magnet. Now test whether both ends of this small strip are equally attracted to the same end of a magnet.
Can you demagnetize a needle?
First magnetize a needle by rubbing one pole of a magnet a few times over the same end of the needle. Rub in only one direction. Test the magnetism by picking up small iron clips. You can destroy the magnetism by heating the needle in a gas flame until it is red hot. (Careful! Use pliers to hold it.) Banging the needle with a hammer or rubbing its poles with a magnet may demagnetize it too.
What you are doing is causing the orderly arrangement of the iron particles to become disarranged. This ruins the magnetism.
What is the best day for static electricity experiments?
Blow up a balloon and tie its mouth. Rub it ten times with a woolen cloth. Place it on the wall. Record how long it stays there. Do it a few times to get the average time. Duplicate the conditions and try it on humid days and on dry days.
Will a magnet pick up a Canadian nickel?
An American 5-cent piece has less nickel in it than a Canadian one. Nickel is a magnetic substance. HINT: Pure nickel is a magnetic metal. Nickel coins, however, contain copper too. United States nickels have less nickel in them than Canadian ones and are therefore less magnetic.
How many miles on a gallon of gasoline?
This is a useful bit of information for your father to know because it gives him an idea of the condition of the car. It also helps him find the cost of a trip he is planning.
Start the test by having the gas tank filled up to the brim while the car is on level ground. It is a good idea to shake the car to remove any air bubbles from the tank.
Copy down the mileage and thereafter keep a record of all the gasoline the tank has added to it. It is not necessary to fill up to the top every time. Continue until at least thirty gallons have been consumed. Of course, the more gasoline you use before ending your test, the more accurate will be the results.
Try to use the same brand of gas and to do just one kind of driving, such as in city traffic or on open highways.
When you are ready to end your test, have the tank filled right up to the brim, again on a level spot. Shake the car as before.
Subtracting the starting mileage from the present mileage will give you the number of miles traveled during the test.
The number of gallons of gas used is what was added during the test, including the amount needed at the end to bring the tank to its original full condition.
Here is a sample test:
Date: June 15 to July 12
Type of driving: City traffic
Miles at end: 20,396.9
Miles at start: 19,652.4
Miles traveled: 744.5
Gallons of gas used: 12 + 6 + 9 + 14 + 10 + 9.4 = 60.4 gallons
Excerpted from Science Research Experiments for Young People by George Barr, John Teppich. Copyright © 1989 Dover Publications, Inc.. Excerpted by permission of Dover Publications, Inc..
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