The purpose of this experiment is to explain the different aspects of static electricity, including effects of electrical charges on small-uncharged objects, electrical attraction and repulsion, creation of electrical charge, practical uses of electrical charges, and measurement of electrical force between electrical charges. Findings Electric current is the flow of electric charge. Some materials become electrically charged when rubbed together. A substance that gains electrons becomes negatively charged, while a substance that loses electrons becomes positively charged.
Charges that are the same (positive and positive or negative and negative) repel, while unlike charges (positive and negative) attract. Charged objects are able to attract small-uncharged objects toward them, such as pieces of paper. Electrical charge can be created by rubbing things
...together or touching them to other objects with greater charge than their own. These properties are demonstrated by the experiments performed in this lab. A styrofoam cup suspended from a fixed support by thread and a second cup are rubbed against hair vigorously.
When they are placed near each other the cups repel each other. They both have the same negative charge. The closer the cups were put toward each other the more they were repelled as evidenced by their threads being pushed apart as well. Electrostatic force increases the closer they are and decreases the further apart they are. When one of these cups was placed very near small-uncharged pieces of paper, they jumped off the table and clung shortly to the cup.
Some electrons are likely to be transferred to the pieces of paper to give them a negative charge and that is why they soon fell of
the negatively charged cup. When a ball of foil is suspended from a string and brought near the second cup, the cup and foil are attracted to each other. At the point they actually touch, they repel each other due to the transfer of electrons from one object to the other. When the negatively charged cup is placed close to a stream of water, the water is so greatly attracted to the cup hat it bends toward the cup. This is because the water is positively charged. Static electricity can and is used to prevent or minimize air pollution. Static charge is applied to dust particles in the air and then collected on a plate of opposite electrical charge. This is called an electrostatic precipitator. Factories use static electricity to reduce pollution coming from their smokestacks. They give the smoke an electric charge. When it passes by electrodes of the opposite charge, most of the smoke particles cling to the electrodes.
This keeps pollution out of the atmosphere. Also air ionizers used in homes work on a similar principle. Our lab experiment demonstrated this when we put the charged cup near a lit cigarette. The smoke was instantly drawn to it. A sock stuck to a sweater in the dryer was taken out. When they were pulled apart, a spark jumped about ? cm. Given that it takes approximately 5000 volts to cause a spark to jump 1 cm. this would indicate that the dryer developed a voltage of 2500 volts.
The electrical force between electrical charges is calculated by Coulomb’s law. The electric force acting on a point charge q1 as a
result of the presence of a second point charge q2 is given by Coulomb's Law: When two pieces of tape were placed on a book and rubbed vigorously then pulled up, they repelled each other because they were negatively charged. When the sock from the dryer was placed near the tape, it was repelled. The styrofoam cup was also repelled. This indicates both the cup and the sock were negatively charged also.
