The floor or similar Essay Example for Free

The floor or similar Essay Prediction: I believe that I will discover that the resistance of a wire increases proportionally with the length. I think that this is due to the way resistance occurs in a typical wire. Resistance is the result of negatively charged electrons (the actual current) colliding with the positively charged ions that make up the wire. The collisions cause the energy in the electron to be lost, and when they occur on a larger scale there is a noticeable difference between the start and end voltage of a circuit. As the length of the wire increases, so must the number of particles. As the number of particles increases, so will the number of collisions, and therefore the amount of resistance encountered. George Ohm discovered that the voltage of a circuit is directly proportional to the current flowing through the circuit, meaning that if you triple one, you triple the other. He then came up with a rule for working out the resistance of a circuit (rearranged from his original equation): Resistance = Current / Voltage This is the formula I will use to calculate the resistance of the wire. A wire, showing collisions occurring If you double the length of the wire, I believe you will double the resistance. Background: The flow of charge in a wire is called the current. It is expressed in terms of the number of coulombs per second going past a given point on a wire. One coulomb/sec equals 1 ampere (symbol A), a unit of electric current named after a French physicist. I have explained how resistance occurs above, and volts are an expression of the amount of energy being carried by the electrons flowing through a circuit. The electrons are negatively charged, and move round the circuit (from the negative side to the positive side of the battery) as a result of attraction to the protons. Plan: I will carry out the experiment by first affixing the 100cm length of the chosen wire to a ruler, using sellotape. I will then set the power supply to approximately the right voltage, and then use the variable resistor to set the exact current (measured on the voltmeter). I have to use this method because the PSU itself is not accurate enough for our purposes. Once this preparation is complete, I will attach the first crocodile clip to one end of the ruler, and the second clip at the first distance, completing the circuit drawn below. The power supply will then be turned on long enough for the measurement to be taken, to prevent the wire heating up. Circuit diagram: Variables and Constants: o The length of the wire, obviously, will change to give a series of readings. o I will also vary the voltage used, to see if the same relationship exists at differing voltages. o The equipment used (see below for list) will all be kept the same, to ensure a fair experiment. o The temperature of the wire I will attempt to keep the same by turning off equipment when not in use. The wire will heat up (as a result of resistance), and so I will give it a chance to cool. Apparatus used: o Meter rule o 1M length of chosen wire, attached with sellotape to above rule. o Crocodile clips o Voltmeter and Ammeter o Standard power supply o Variable resistor o Connecting cables Safety Considerations: o The wire will heat up during the experiment, so care must be taken to ensure it does not burn. The current will only be left on for the minimum amount of time, to prevent dangerous heating. o Some wires available are very thin but strong, and can cut easily into flesh. o Trailing cables are a hazard, and I must make sure no cables drape onto the floor or similar.

Analysis of Bruce Springsteens Song Devils & Dust Essay -- Song Music

Analysis of Bruce Springsteen's Song "Devils & Dust" In times of war it is quite common for people to start questioning their values and their actions and be unsure of the path they are taking. This is common because to protect our values we often are told that we have to take actions that conflict with those values. One example would be how to protect our liberties we must sometimes restrain those liberties during treacherous times. However, the ultimate question is whether or not going against the very values we stand for is a hypocritical and wrongful action plan. Bruce Springsteen approaches this very issue in his song â€Å"Devils & Dust†, from the CD with the same title, and he subtly criticizes how the United States is betraying its values. Springsteen wrote â€Å"Devils & Dust† during the Iraq War. He has been openly against the war and has been quoted saying to Rolling Stone, â€Å"As the saying goes, "The first casualty of war is truth." I felt that the Bush doctrine of pre-emption was dangerous foreign policy. I don't think it has made America safer.† The song itself could be interpreted as a soldier’s point of view about the war but overall it stands as a critique on our society betraying its own principles. The first couple of verses in the song already evoke the image of a soldier stuck in a war. â€Å"I got my finger on the trigger / But I don’t know who to trust† could be understood as a soldier’s experience in war but it could also have a deeper meaning. It could also signify that our society has to make these important choices that will end up affecting people’s lives but it is all too ambiguous, there just isn’t any certainty. We are left w ith the desperate feeling of not knowing what to do, not knowing wh... ...ty and privacy are essential for it. Also, I am a dual citizen and in my other country, which is Brazil, we are still somewhat haunted by the shadow of a dictatorship that just ended in 1987. So I know people who have suffered the consequences of lack of liberty. Even so sometimes I am doubtful of my opinion, even though I try not to express it often and defend liberty as much as I can. Whenever I see some terrible act, whether terrorist or governments do it, I think if there would be a way to stop that with restrictions on certain liberties and more surveillance. However, if we do that, if we overreact, we destroy our values, destroy a part of ourselves and fill our soul with devils and dust. Works Cited Springsteen, Bruce. â€Å"Devils & Dust.† Devils & Dust. Columbia Records, 2005. Springsteen, Bruce. â€Å"We’ve Been Misled.† Rolling Stone 22 Sep. 2005

Analysis of 2 commercial brands Essay

Topic : Analysis of 2 commercial brands of bleaching solution & a determination of the best buy Introduction : Sodium chlorate(I) forms the basis of most commercial bleaches. The amount present in bleaching solution can be determined by a volumetric technique. In this experiment, sodium chlorate(I) reacts with excess potassium iodide in the presence of acid to liberate. The iodine is titrated against standard sodium thiosulphate solution. Chemicals : Bleach solution , 0.1 M Na2S2O3 ,1 M H2SO4 , KI , Starch indicator  Procedures : 1. Determine the total volume of bleach in the commercial bottles provided. Note the brand name, volume & price of each sample. 2. Pipette 25 cm3 bleach solution into a 250 cm3 volumetric flask. Make up to the mark & mix well. 3. Pipette 25 cm3 of this solution into a conical flask. Add 10 cm3 KI solution & 10 cm3 1 M sulphuric acid. 4. Titrate this mixture against the standard sodium thiosulphate solution provided. Add starch indicator when the solution become pale yellow. 5. Record your results and calculate the molarity of the orginal bleach solution. 6. Determine which bleach has the lowest price per mole of actual bleach. Results : Brand A = ___________KAO_____________ Brand B = _________Best Buy____________ Volume = ___________1.5L______________ Volume = ____________2L_______________ Price = _______$12.9 / Bottle____________ Price = ________$10.9 / Bottle____________ Mole = _________0.753 Mol_____________ Mole = ___________1.152 Mol ___________ $/mole = _______$17.13 / Mol ___________ $/mole = __________$9.46 / Mol__________ Best buy is ________ Best Buy___________ Titration of Brand A against the standard sodium thiosulphate solution Titration 1 2 3 4 Final Burette Reading (ml) 31.70 35.70 27.80 32.20 Initial Burette Reading (ml) 2.90 9.80 4.40 8.30 Volume of titrant (ml) 28.80 25.90 25.40 23.50 Mean volume of titrant (ml) = __(25.90+25.40+23.50)à ¯Ã‚ ¿Ã‚ ½3 = 25.1 ml__ Calculation: The Result Of Brand A Sodium chlorate(I) reacts with excess potassium iodide in the Bleaching solution, which is a acid medium. Iodine solution produced. Following equation: 2H+-(aq) + OCl–(aq) + 2I–(aq) –> Cl–(aq) + I2-(aq) + H2O-(l) Secondly, the iodine solution is titrated with sodium thiosulphate solution Following equation: I2(aq) + 2 S2O32- (aq) –> S4O62- (aq) + 2 I-(aq) The Molarity of Na2S2O3 : = 0.1M Number of mole of S2O3- reacted with I2: : = Molarity X Volume = 0.1 X (25.1à ¯Ã‚ ¿Ã‚ ½1000) = 0.00251 mol The Mole ratio of Na2S2O3:: I2= 2:1 Number of moles of I2 reacted with S2O3- = (1à ¯Ã‚ ¿Ã‚ ½2) X 0.00251 mol = 0.001255 mol The Mole ratio of NaOCl: I2= 1:1 Number of moles of NaOCl used in the titration = I2 = 0.001255 mol Number of moles of NaOCl in the 250ml volumetic flask = 0.001255 mol X 10 = 0.01255 mol Number of moles in 1.5L bleach solution = 0.01255 mol à ¯Ã‚ ¿Ã‚ ½ 25 X 1500 = 0.753 mol Price of OCl- per mole in brand A = $12.9 à ¯Ã‚ ¿Ã‚ ½ 0.753mol = $17.13 / mol Results : Titration of Brand B against the standard sodium thiosulphate solution Titration 1 2 3 4 Final Burette Reading (ml) 30.90 32.8 31.90 35.20 Initial Burette Reading (ml) 2.10 3.90 3.30 6.90 Volume of titrant (ml) 28.8 28.90 28.60 28.90 Mean volume of titrant (ml) = __(28.90+28.60+28.90)à ¯Ã‚ ¿Ã‚ ½3 = 28.8 ml__ Calculation: The Result Of Brand B Sodium chlorate(I) reacts with excess potassium iodide in the Bleaching solution, which is a acid medium. Iodine solution produced. Following ionic equation: 2H+-(aq) + OCl–(aq) + 2I–(aq) –> Cl–(aq) + I2-(aq) + H2O-(l) Secondly, the iodine solution is titrated with sodium thiosulphate solution Following ionic equation: I2(aq) + 2 S2O32- (aq) –> S4O62- (aq) + 2 I-(aq) The Molarity of Na2S2O3 : = 0.1M Number of mole of S2O3- reacted with I2: : = Molarity X Volume = 0.1 X (28.8à ¯Ã‚ ¿Ã‚ ½1000)= 0.00288 mol The Mole ratio of Na2S2O3:: I2= 2:1 Number of moles of I2 reacted with S2O3- = (1à ¯Ã‚ ¿Ã‚ ½2) X 0.00288 mol = 0.00144 mol The Mole ratio of NaOCl: I2= 1:1 Number of moles of NaOCl used in the titration = I2 = 0.00144 mol Number of moles of NaOCl in the 250ml volumetic flask = 0.00144 mol X 10 = 0.0144 mol Number of moles in 2L bleach solution = 0.0144 mol à ¯Ã‚ ¿Ã‚ ½ 25 X 2000 = 1.152 mol Price of OCl- per mole in brand B = $10.9 à ¯Ã‚ ¿Ã‚ ½ 1.152 mol = $9.46 / mol Questions : 1. Why must the KI be present in excess ? If less than the specified quantity of KI is added, what effect will this have on the results ? The bleach solution contain sodium chlorate(I),which have ions OCl-.We can prepare the iodine solution by adding the sodium chlorate(I) to potassium iodide in a acidic medium. At first, the sodium chlorate(I) Is the limiting agent. When we add the excess potassium iodide into the bleach solution. Not only it will not effect the result, but also the calculation can be more accurate. All the ions OCl- can be completely reacted. In addition, Iodine solution is only slightly soluble in water but it is very soluble in the solution, which contain I- ions. 2. What is the function of the sulphuric acid ? The function of sulphuric acid is provide a acidic medium containing excess iodide to ionizes the iodine solution to triiodide ions. We must know that the Brown colour of iodine solution is cause for the triiodide ions(I3-).This colour in observation of titration is very important. 3. Bleaching solutions may deteriorate for 2 reasons : (a) react with CO2 in the air according to the equation : 2 OCl- + CO2 –> CO32-+ H2 + Cl2 (b) what is the other reason ? It must be effected by light. It is because the The hypochlorite ions OCl-( will be decompose quickly under light Following equation:2NaOCl –>2NaCl + O2, .While losing some OCl- ions, the result in calculation will not be accurate 4. What should the starch indicator not be added too early ? The starch solution turns the iodine to blue black because of the formation of starch-iodine complex. Also, the complex is not reversible when the concentration of iodine is high. If we add the starch solution early, the attraction of starch molecules and iodine molecules will attract so strongly. Although we have add standard sodium thiosulphate solution, but we can not do completely finish the real result of titration and effecting the calculation. The above-mentioned tell us that the starch solution should be added when only a few of iodine solution left, near the end point of the titration. Conclusion: The bleach solution of brand B is the best buy.

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