![]() ![]() It is grounded by means of the movement of electrons from the ground to the aluminum plate. When the aluminum-covered straw is touched, the aluminum plate loses its charge. One straw is covered with aluminum foil and the other straw is bare plastic. A common lab activity involves taping two straws to a charged aluminum plate. The person is an effective ground because it has enough size to share the overwhelming majority of excess positive charge.Īny object can be grounded provided that the charged atoms of that object have a conducting pathway between the atoms and the ground. And once again, the extent to which an object is willing to share excess charge is proportional to its size. ![]() The excess positive charge is shared between the electroscope and the ground. As in the case of grounding a negatively charged electroscope, the grounding of a positively charged electroscope involves charge sharing. While this may disrupt any balance of charge present on the person, the significantly larger size of the person allows for the excess charge to distance itself further from each other. This process works because excess positive charge on the electroscope attracts electrons from the ground (in this case, a person). Thus, the grounding of a positively charged electroscope involves the transfer of electrons from the ground into the electroscope. By gaining electrons from the ground, the electroscope will have a balance of charge and therefore be neutral. A positively charged electroscope must gain electrons in order to acquire an equal number of protons and electrons. But what if the electroscope is positively charged? How does electron transfer allow an object with an excess of protons to become neutralized? To explore these questions, we will consider the grounding of a positively charged electroscope. Electrons were transferred from the electroscope to the ground. The previous discussion describes the grounding of a negatively charged electroscope. So an effective ground is simply an object with significant enough size to share the overwhelming majority of excess charge. The extent to which an object is willing to share excess charge is proportional to its size. Like contact charging discussed earlier, grounding is simply another example of charge sharing between two objects. Because of the relative size of a person compared to a typical electroscope, the excess electrons (nearly all of them) are capable of reducing the repulsive forces by moving into the person (i.e., the ground). This spatial separation is achieved by moving to a larger object that allows a greater surface area over which to spread. As is always the case, repulsive affects between like-charged electrons forces them to look for a means of spatially separating themselves from each other. This process of grounding works because excess electrons find each other repulsive. These excess electrons subsequently spread about the surface of the person. Upon contact, the excess electrons leave the electroscope and enter the person who touches it. ![]() In typical electrostatic experiments and demonstrations, this is simply done by touching the electroscope with one's hand. To remove the excess of electrons from a negatively charged electroscope, the electroscope will have to be connected by a conducting pathway to another object that is capable of receiving those electrons. Once the excess electrons are removed from the object, there will be equal numbers of protons and electrons within the object and it will have a balance of charge. If it is to have its charge removed, then it will have to lose its excess electrons. Any negatively charged object has an excess of electrons. To begin our discussion of grounding, we will consider the grounding of a negatively charged electroscope. In this last section of Lesson 2, the process of grounding will be discussed. A ground is simply an object that serves as a seemingly infinite reservoir of electrons the ground is capable of transferring electrons to or receiving electrons from a charged object in order to neutralize that object. When a charged object is grounded, the excess charge is balanced by the transfer of electrons between the charged object and a ground. Grounding is the process of removing the excess charge on an object by means of the transfer of electrons between it and another object of substantial size. Objects with an excess of charge - either positive or negative - can have this charge removed by a process known as grounding. A discussion of charging would not be complete without a discussion of uncharging. The previous three sections of Lesson 2 discussed the three common methods of charging - charging by friction, charging by induction, and charging by conduction. ![]()
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