3. Suspend a U tape from a thread or a hair. Hold the thread or hair in your han

Question

3.   Suspend a U tape from a thread or a hair. Hold the thread or hair in your hand, or use a short piece of tape to stick the upper end of the thread or hair to the meterstick. Approach the suspended tape from various directions with another U-tape. Do you find that the force does indeed act along a line drawn from one object to the other?

Summary: Forces act along a line connecting the charged objects!

4.   Move a U tape very slowly toward another hanging U tape. Observe the deflections of the tapes from the vertical, at several distances (for example the distance at which you first see repulsion, half that distance, etc.) Make a very rough graph of the strength of the repulsive interaction as a function of the distance between the two tapes (you can’t really go all the way to zero distance!).

Strength of
force

   0                      
Distance

The deflections of the tapes away from the vertical is a measure of the strength of the interaction. Does the force decrease rapidly as the distance between the tapes increases?

Summary: Force decreases rapidly as the distance between the tapes increases!

You may have already discovered that if you handle a U tape too much, it no longer repels another U tape. Next, we will learn a systematic way for making this happen.

5.   Make sure that you have an active U tape, by seeing that it is attracted to your hand. Then, holding onto the bottom of the U tape, slowly rub your fingers or thumb back and forth along the slick side of the tape. Describe the changes in how this U tape no longer interacts with your hand.

You should find that the U tape no longer interacts with your hand, so we have a way of making a tape not interact with other ordinary objects, which will be useful in the future. If the U tape was electrically charged as we suppose (presumably on its sticky side), then by running a finger along the slick side we have apparently “neutralized” it – it now appears electrically neutral (uncharged).

6.   Let’s partially neutralize a U tape and see what happens. Prepare two charged U tapes.
   Hang one of them from the meterstick, and note how strongly the other tape repels it.
   Partially neutralize one of the tapes by running your finger along the length of the slick side of the tape, being careful that your finger touches only a portion of the width of the tape.
   Again observe how strongly the two tapes repel. What is the effect of this partial   neutralization?

You should observe that the two tapes repel less strongly when you partially neutralize one of them. For now, you can see that to a certain extent we can control the amount of “charge” on a tape, and that the force between two tapes seems to depend on the amount of charge on each tape.

There are two types of charges that appear in nature. How could you prepare a tape that might have an electrical charge unlike the charge of a U tape?

Perhaps you reasoned along these lines: We don’t know how the U tape became charged, but if the tapes started off neutral, maybe the U tape pulled some charged particles off of the bottom tape (or vice versa). So, now the bottom tape might have an equal amount of charge, of the opposite sign.

Explanation / Answer

There are two types of materials present. One, "The Conductor" through which electricity flows, or the charges can move freely. And the other "The Insulator" which resists the flow of charges. The U tube, by analyzing its properties, it is more likely to be an insulator. When an insulator is in contact with a conducting material, it looses the charge and becomes neutral. To avoid this the best way to preserve the charge loss, is to coat a thin layer on the U tube with another insulating material, like plastic. This makes sure that the charge does not leave the surface while repelling other charges present around.

But to initially charge the U tube, there are many ways to do it. We can pull off weak electrons from the outer most layer by using friction. or we can spray charged oil on the U tube, etc. These wil charge the U tube. Once that is done, coating it with a this insulating material will make sure the charges wont escape.

I hope the answer is helpful.

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