the final answers are already there, but can i get the steps on how to get the r
ID: 1881185 • Letter: T
Question
the final answers are already there, but can i get the steps on how to get the right answers
1) On a very cold dry February day a long haired student who is wearing wool clothing is scuffing his way across a carpeted room. He notices an electroscope, a piece of plastic pipe and a piece of wool flannel on a table.
a. Explain how he could use these pieces of apparatus to determine if he had picked up a charge from the carpet.
b. Explain how he could use these pieces of apparatus to determine the polarity of whatever charge he had picked up from the carpet.
2) In 1976, Neher and Sackmann invented the “patch clamp” method of experimentally investigating the electric currents that are represented by ions moving through cell membrane ion channels. This method allows for the measurement of currents as low as 1pA. Assume that this current is carried by sodium ions and determine how many sodium ions pass through this channel during 1ms (a reasonable estimate of the amount of time that an individual sodium ion channel remains open).
3) Nickel plating is a process whereby a piece of jewelry, like an ID bracelet, may be given a surface that will not corrode and will remain shiny for many years. The piece of jewelry is connected, by a wire, to one terminal of a battery, and then is immersed in a solution of nickel- chloride (NiCl2). A piece of pure nickel is connected to the other terminal of the battery and is also placed into the solution. In the solution, the following chemical reaction takes place:
NiCl2 Ni++ + 2 Cl-
Assume that 0.5 grams of nickel are to be plated onto the piece of jewelry. Assume also that 20A
of current flow through the solution while the piece of jewelry is being plated.
a. To which terminal of the battery should the piece of jewelry be connected? You must
explain your answer. (Negative)
b. How many atoms of Ni will be plated onto the jewelry during this process? (5.085x1021) c. How much electric charge will flow through the solution during this process? (1627C) d. For how long should the current be allowed to flow? (81.3s)
4) A light bulb, when connected to a 12V battery, uses5J of electric energy each second.
a. How many electrons pass through the light bulb in 15 minutes? [2.34x1019 electrons] b. Calculate the resistance of the light bulb under the conditions described above. [29]
5) As we have discussed in class, the cell membrane of animal neurons is slightly “leaky” to K+. A reasonable value for the resistance of a small section of the membrane material of
ahuman neuron is 13k. The normal voltage across such a membrane is 70mV. Given theseconditions, calculate how many grams of K+ ions would leak through such a membrane during 1 second? [2.19ng]
6)
Lidocaine (C14H22N2O) is a commonly used anesthetic. As a preliminary step when applying an IV to a child, lidocaine may be administered in order that the child not “feel” the pain caused by the insertion of the IV. In order to introduce the lidocaine in a way that will be localized but will not be painful, iontophoresis may be used. In this process, two electrodes are placed on the child’s skin; one near to the site of the IV and the other several cm away. Ionized lidocaine, C14H23N2O +, is placed under one of the electrodes. A DC current of 1.2mA is the applied to the electrodes.
a. To which electrode, positive or negative, should the ionized lidocaine be applied? EXPLAIN your answer. [POSITIVE]
b. For how much time should the iontophoresis continue in order that 5mg of the anesthetic will be introduced into the child? [28 MINUTES]
c. What DOSE of lidocaine had been applied during this treatment? [34 mA min]
Explanation / Answer
1) Static electricity is generally high in cold and dry waethers. The static charge may dissappear in humid conditions. When the girl walks on the carpet, she rubs the carpet and the electrons get transferred to her body. Therefore, she charges her body with electrons she cannot get rid of , which also get transfered to her long hair. This leaves the girl to be slightly negatively charged.
a) She has to first rub the plastic piece with the wool fannel. This charges the apparatus by transfering the electrons from the plastic peie to the wool fannnel making the plastic peice positively charged. In order to determine if her body is charged she has to take the woolen fannel and move it near her hair, if the woolen fannel repels , it means that she is charged with electrons .
b) If the fannel does not repel she is not charged and is neutral in nature.BUt if the wollen fannel repels against her hair , it means that she is negatively charged.
SHe can get rid of the charge by moving the plastic piece over her hair, so that all the electrons get tranfered from her body to the plastic piece.
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