Why Do Rubbed Materials Attract or Repel Each Other?

[zaftcouncil]

1. When a piece of cellulose acetate (transparency) is rubbed by stroking it for about 10 to 20 times in one direction and brought towards a piece of rubbed polythene strip,

i. state what happens, and
ii. explain the observation.

2. Before rubbing a polythene strip with a soft cloth, both the strip and the cloth are neutral. After rubbing, the polythene strip is charged negatively.

a. Does a neutral body possesses any charge? Explain.
b. Is the soft cloth charged after rubbing? If it is, is it charged positively or negatively?
c. How do you discharge an insulator like a polythene strip?

Thanks in advance.

 

[HallsofIvy]

1. The question asks what YOU observe. No one else can tell you that! Go ahead and DO the experiment and see what happens.

2. What do YOU think? Part (a) certainly should be easy. These are just a matter of knowing the definitions.

 

[wais]

1. When the rubbed cellulose acetate is brought towards the rubbed polythene strip, the two materials will attract each other and stick together. This is due to the build-up of static electricity, which causes opposite charges to attract each other. The cellulose acetate becomes positively charged while the polythene strip becomes negatively charged. This is known as the triboelectric effect, where two materials rubbing against each other transfer electrons and create static charges.

2. a. No, a neutral body does not possess any charge. This means that it has an equal number of positive and negative charges, which cancel each other out and result in a net charge of zero.

b. Yes, the soft cloth will also become charged after rubbing. However, the type of charge depends on the materials involved. In this case, since the polythene strip becomes negatively charged, the soft cloth will become positively charged.

c. To discharge an insulator like a polythene strip, you can use a grounding wire or a grounding mat. By connecting the insulator to a conductive surface, the excess charge will flow through the conductor and neutralize the insulator. Another method is to use a discharge wand, which is a pointed metal object that can be touched to the insulator, allowing the excess charge to escape.

 

[wais]

1. When the cellulose acetate is rubbed and brought near the rubbed polythene strip, they will attract each other. This is due to the buildup of static electricity on the surfaces of both materials. The rubbing process causes the transfer of electrons between the two materials, leaving one with a positive charge and the other with a negative charge. This attraction is observed because opposite charges attract each other.

2. a. No, a neutral body does not possess any charge. This means that it has an equal number of positive and negative charges, resulting in a net charge of zero.

b. Yes, the soft cloth will also become charged after rubbing. It will have the opposite charge of the polythene strip, so it will be charged positively.

c. To discharge an insulator like a polythene strip, it can be touched by a conductor, such as a metal object. This will allow the excess electrons to flow from the polythene strip to the conductor, equalizing the charges and discharging the strip. Another method is to place the insulator near a high-voltage source, which will cause the excess electrons to jump from the insulator to the source, again equalizing the charges and discharging the insulator.