In pan C of the experiment, an electrophorus will be used to get more charge tha
ID: 3161665 • Letter: I
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In pan C of the experiment, an electrophorus will be used to get more charge than we can from rubbing rods. An electrophorus is a metal disk (grey in the diagram below) with an insulating handle (black in the diagram below). Suppose that you have a plastic sheet that has already been positively charged by being rubbed with a cloth. The rubbed side of the sheet is placed face-down. What will happen to Actually, the glass flask that encases an electroscope becomes charged after some time. If enough charge appears on the glass flask, then the electroscope doesn't respond as we expect. Use your second electroscope in these cases. In the meantime, the casing of the first electroscope will lose its charge and again behave as you expect. charge in the electrophorus if it is put on the charged plastic sheet? Explain in words what will happen. Copy the following diagram in your pre-lab and indicate the charged regions. |3| Let's think about a different situation before returning to the electrophorus. 'Ground' is just what you think: The Earth. Suppose that a (small) charged conductor Is connected to ground. Explain why the conductor becomes uncharged. |2| [It might help for you to replace the word 'ground' with the phrase 'a really big nail'. In electrostatics I, you thought about what is happening to charge inside a nail when a charged object approaches it.] Let's return to the electrophorus. Typically, the charged plastic sheet is on a bench and the electrophorus is put on top of it. The top surface of the METAL disk of the electrophorus is briefly connected to ground and then disconnected from it. What is the charge-state of the electrophorus after the electrophorus is momentarily connected to ground and then disconnected from it? [1] Explain, assuming that the positive charge is free to move. [2] Imagine the charge-state of the electrophorus is as in the previous paragraph before any connection to ground is made. Now let's change our perspective. Your previous explanation assumed that positive charge was free to move. Now assume that positive charge is stationary and that negative charge moves. Using this assumption to explain the charge-state of the electrophorus after the electrophorus is momentarily connected to ground and then disconnected from it. |2|Explanation / Answer
1. As plastic sheet is positively charged it will induce negative charge on the cotact surface of the electrophorus while positive charge at the top surface of the same.
2. Earth is considered as the infinite sink and so any charged conductor connected with Earth will have zero charge as all the charge will flow to the ground and it will achieve the same potential as the Earth which is zero and thus will reach the zero potential difference until the charge flow stops.
Now let's assume Earth with long nail which is at zero potential and if it gets connected with the charged conducter, charge will flow till it achieve the same charge density which is zero being a very long nail and so we can easily replace earth with very long length nail with zero prerenial potential.
[1]. As the Electrophorus is momentarily connected with ground, all positive charge on the top surface will travel to the ground and once it is disconnected then it will have net Negative charge on the lower surface which is bound with the positive charge of the plastic sheet.
[2].In the previous case Negative charge of the Electrophorus is bound with positive charge of the plastic sheet and so the positive charge of the elctrophorus is free to move. In reverse, if negative charge is free to move which is only possible if positive charge is bound with the Negative charge of the plastic sheet and in that case negative charge will flow to the ground and elctrophorus will become positively charged. So, the condition for positive charge of the Electrophorus in bound state is that Plastic sheet is Negatively charged.
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