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SCIENCE COURSEWORK: RESISTANCE OF WIRE EXPERIMENT
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Risk Assessment To keep the experiment safe I shall keep electrical conductors away from the plug sockets. I will take care not to hurt myself or anybody else with the crocodile clips. I will also not turn the power socket on full so as that the wire does not burn or set fire to any surrounding objects or burn anybody. Preliminary work Firstly I assembled the apparatus as shown in the diagram below. For the wire I used 34 standard wire gauge wire. I then took measurements placed the two wire ends marked with an X...
Voltmeter reading by the Ammeter reading, giving me the resistance. This experiment would then be repeated three times so as to determine any anomalous results.

Diagram of apparatus for alternative experiment

I predict that the readings on the Voltmeter and Ammeter would be higher but when divided and the resistance worked out that the resistance would be very similar to that of the results worked out in my main experiment. This would be a useful experiment to carry out alongside my other to support my theory and satisfy my aim.

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Physics Investigation Of Resistance Aim:...Physics Investigation Of Resistance Aim: to investigate how the electrical resistance of a wire changes in relationship to it´s length. Prediction: I think that as the length of the wire increases so to will the resistance of it. I also believe that the rate at which the resistance of the wire increases will be directly proportional to the length. The graph to show this should therefore look something like this: Reason: with electricity, the property that transforms electrical energy into heat energy, in opposing electrical current, is resistance. A property of the atoms of all conductors is that they have free electrons in the outer shell of their structure. All metals are conductors and have an arrangement in similar form to this: As a result of the structure of all conductive atoms, the outer electrons are able to move about freely even in a solid. When there is a potential difference across a conductive material all of the free electrons arrange themselves in lines moving in the same direction. This forms an electrical current. Resistance is encountered when the charged particles that make up the current collide with other fixed particles in the material. As the resistance of a material increases so to must the force required to drive the same amount of current. In fact resistance, in ohmsR is equal to the electromotive force or potential difference, in volts V divided by the current, in amperes I "“ Ohm´s law. As the length of the wire is increased the number of collisions the current carrying charged particles make with fixed particles also increases and therefore the value for the resistance of the wire becomes higher. Resistance, in ohms R is also equal to the resistivity of the wire, in ohm-meters ñ multiplied by the length, in meters l divided by the cross sectional area, in square meters A. The material and cross sectional area of the wire is constant throughout the experiment. Therefore it is clear from the formula that the resistance should be directly proportional to the lengthKey factors: in this experiment we will only change one factor, the length of the wire. This should effect the resistance of the wire in the ways stated above. Fair test: in this experiment we are only changing one factor "“ the length of the wire, the factors that we are going to keep the same are as follows: We must keep the surrounding room temperature the same or the particles in the wire will move faster if the temperature is increased and this will therefore have an effect on the resistance. The cross sectional area of the wire must be kept constant throughout as well. This is shown in equation 2 where the cross sectional area is a factor that effects the resistance. The material of the wire must also be kept the same as different materials have different conductivity. The last two factors will be kept the same by using the same wire all of the way through the experiment. The current that we pass through the wire is to be kept the same, also. If this is changed the temperature of the wire might change in a way that is not constant making the results more confusing. Apparatus: 1. Wire, over 50 cm long 2. Rheostat 3. Power supply 4. Six connecting wires 5. Two crocodile clips 6. Voltmeter 7. Ammeter Plan: 1. Connect circuit as shown in the diagram. 2. Adjust rheostat until the ammeter reads .3 A. 3. Record voltage on voltmeter 4. Repeat the experiment with the following lengths of wire, connected between the two crocodile clips: - 10 cm - 15 cm - 20 cm - 25 cm - 30 cm - 35 cm - 40 cm - 45 cm - 50 cm 5. Use Ohm´s law to find the resistance of the wire, equation 1. Diagram: Safety: this is not a very dangerous experiment but despite this you must always handle electricity with care, keep the current low, handle with dry hands etc. Accuracy: to keep this experiment as accurate as possible we need to make sure, firstly, that the length of the wire is measured precisely from the inside edge of the crocodile clips, making sure that the wire is straight when we do this. We must also make sure that the wire is straight when we conduct the experiment. If it is not, short circuits may occur and bends and kinks in the wire may effect the resistance, also. The reading that we take of the voltage should be done fairly promptly after the circuit is connected. This is because as soon as a current is put through the wire it will get hotter and we want to test it when heat is effecting it the least, i.e. at the beginning Preliminary: upon testing to see if the experiment would work I found no problems with the plan I described earlier. I was able to get the following results: LENGTH cm CURRENT A VOLTAGE V RESISTANCE =V/IÙ 10 0.3 0.13 0.43 15 0.3 0.20 0.66 20 0.3 0.27 0.90 25 0.3 0.35 1.16 30 0.3 0.42 1.40 35 0.3 0.48 1.60 40 0.3 0.57 1.90 45 0.3 0.60 2.00 50 0.3 0.68 2.26 Observations Observations: we will observe the reading on the voltmeter change as we change the current to .3 A. we also observe a general increase in the voltage as the length of wire we use gets longer. The rheostat will also be set at different positions for the different lengths of wire that we use. Evidence: to make sure our overall values are as accurate as possible we will repeat our readings 3 times and then take the mean resistance of the 3 readings. We will also be able to spot and discard any anomalies from our results. Results: Set i Length cm Current A Voltage V Resistance =V/I in Ù 10 0.3 0.13 0.43 15 0.3 0.20 0.66 20 0.3 0.27 0.90 25 0.3 0.35 1.16 30 0.3 0.41 1.36 35 0.3 0.48 1.60 40 0.3 0.56 1.86 45 0.3 0.62 2.06 50 0.3 0.69 2.30 Set ii Length cm Current A Voltage V Resistance =V/I in Ù 10 0.3 0.13 0.43 15 0.3 0.20 0.66 20 0.3 0.27 0.90 25 0.3 0.35 1.16 30 0.3 0.42 1.40 35 0.3 0.49 1.63 40 0.3 0.57 1.90 45 0.3 0.61 2.03 50 0.3 0.70 2.33 Set iii Length cm Current A Voltage V Resistance =V/I in Ù 10 0.3 0.13 0.43 15 0.3 0.20 0.66 20 0.3 0.28 0.93 25 0.3 0.34 1.13 30 0.3 0.40 1.33 35 0.3 0.48 1.60 40 0.3 0.57 1.90 45 0.3 0.62 2.06 50 0.3 0.70 2.33 Average Length cm Resistance Ù-Set i Resistance Ù-Set ii Resistance Ù-Set iii Mean Resistance Ù 10 0.43 0.43 0.43 0.43 15 0.66 0.66 0.66 0.66 20 0.90 0.90 0.93 0.91 25 1.16 1.16 1.13 1.15 30 1.36 1.40 1.33 1.38 35 1.60 1.63 1.60 1.61 from 40 1.86 1.90 1.90 1.89 45 2.06 2.03 2.06 2.05 50 2.30 2.33 2.33 2.32 Anomalies: there was only one real anomaly in this experiment and it has been highlighted like this: 000 Analysis Trends: from the graph we can see one very clear trend, which is, as the length of the wire increases so does the resistance of it. Another, more significant thing is that it the increase is constant. This is indicating by the fact that the line drawn is a straight one. One may also note that the gradient of the line drawn is 1.85/40 .04625. Conclusion: I think that from my results I can safely say that my prediction was right. The resistance did change in proportion to the length. This is because as the length of the wire increased the electrons that made up the current, had to travel through more of the fixed particles in the wire causing more collisions and therefore a higher resistance. We can work out what the resistivity of the wire should be from our results using the It is obvious from the formula that R/l is simply the gradient of the graph, therefore Evaluation I feel that overall our results were quite accurate. This is can be seen when we look at the graph, which shows a straight line with all of the points apart from one being very close to or on that line. The one point that was not that close to the line was a slight anomaly, but it was only slight and did not effect the final gradient of the graph. I have found out that for the wire I was using, the resistivity at 20©C is 4.9 X 10-7 ohm-meter. From this we can then work out the percentage error of our results: The accuracy for this experiment is, theoretically, ± 15.7%, but as one can see this does not seem to be the case from looking at the graph. The reason for this could have been due to a number of different factors. Firstly the temperature of the wire was not necessarily 20©C when we conducted the experiment and the material of wire may not be as pure as it should have been. The main reason for this was probably due to the equipment that we used being inaccurate. This did not stop us from seeing the trend, though, because the equipment would have been out by a constant amount each time therefore there was a constant error. So the trends that were predicted in the plan still were shown. Most errors in our experiment were encountered in the measuring of the wire. This is because it simply was not very practical to hold a piece of wire straight, whilst holding it next to a ruler and then trying to accurately fix crocodile clips to the right part on the wire. Also I do not feel that the crocodile clips were always fixed securely to the wire with a good connection. This also meant that they were easy to move about on the wire changing the length of it. Errors rarely occurred in the setting of the current and the reading of the voltage. It was just in the preparation area that they did occur. Another example of this is the wire was never totally straight when we started the experiment, which may also, as said earlier on, effect the resistance of it I do not think that doing any more results in our experiment would have made it any more accurate. I feel that the only way to make it more accurate would be to use a different method "“ perhaps were we had a bar that did not bend in place of the wire. We could even use a rheostat in place of the wire, because it is essentially a long coiled wire that is connected at different lengths to change the resistance of the circuit   

Physics Investigation Of Resistance Aim: to investigate how the electrical resistance of a wire changes in relationship to it´s length. Prediction: I think that as the length of the wire increases so to will the resistance of it. I also believe that the rate at which the resistance...

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My aim is to... My aim is to find out whether temperature has an effect on a rate of the reaction. I am going to be using the example of the reaction between Sodium Thiosulphate and Hydrochloric Acid. Prediction I predict that the higher the temperature, the more quickly the reaction will occur. This is because with heat, the particles of sodium thiosulphate and hydrochloric acid have more energy. This causes them to move around more. It works like this for all substances, not just those two. Chemical reactions require collisions, and if particles are moving around more quickly they are obviously more likely to collide and, as Collision Theory states, it affects the energy of the collision. I found out from preliminary research that the particle theory explains that chemical reactions require a collision between the particles of the reactants, at a certain speed and energy. I also found out that the factors that affect the rate of a reaction are:- § The surface area of the solid reactant if there is one § The concentration of the liquid substance. § The presence of a catalysts § The temperature In this experiment we are only interested in temperature. Where temperature is not high enough to provide energy for the particles to move at a high enough speed, the particles will just not react, and the higher the temp. the faster the particles move, so there are more collisions and so the faster the reaction will take place. At 20°C, I predict that the reaction will take a very long time to react. The reason I think this, is because although the particles will be moving around, they will not be moving at a high enough velocity for chemical reactions to occur, the particles must be travelling at a high speed and this requires energy. At this temperature I do not think that it will give the particles enough energy to convert into movement. At 30°C, I predict that the reaction will occur more quickly than that of 20°C. I predict this because there is more heat to provide energy to the particles of the reactants. This energy causes the particles of sodium thiosulphate and hydrochloric acid to move around more quickly, and naturally more collisions happen between the particles. Every jump upwards in the temperature of ten degrees I would expect the rate of the reaction to double. It should follow the Q10 rule. At the highest temperature of 60°c I would expect the reaction time to be very fast. I think this because the particles of sodium thiosulphate and hydrochloric acid will be moving around very quickly and at a high velocity so the chemical reaction will take place quicker. To summarise, at a cold temperature the reaction will take more time to happen. The particles of sodium thiosulphate and hydrochloric acid will not be moving around so quickly, meaning they are less likely to collide, therefore the reaction will take place in more time. Chemical reactions require a collision at a certain velocity, and if this velocity is not reached then the reaction will just not happen. With more heat, the particles have more energy, meaning they move around more. Collisions will be more likely to happen at a higher speed. Rate = Results. Temp. °C 20 30 40 50 60 Time s 1. 69 33 35 13 08 2. 62 32 35 12 12 3. 42 24 29 10 10 Average 65.5 32.5 29 11.66 10 Rate 0.015 0.030 0.034 0.085 0.100 Number = anomaly See graph 1.A Higher temperature has two effects: - - More collisions per second, - More energetic collisions. That's why a 10°C rise doubles the rate rather than double temp doubles rate. Conclusion I conclude that the temperature does affect rate of reaction "“ the higher the temperature the faster the rate of reaction. I can see this from my table the lowest temperature has the highest reaction time - 20°C took 57s "“ and the highest temperature has the quickest reaction time - 60°C took 10s. as my graph shows. The line of best fit goes up very steeply. This is because with more heat, the particles of sodium thiosulphate and hydrochloric acid have more energy. This causes them to move around more. Chemical reactions require collisions, and if two sets of particles are moving around quickly there will naturally be more collisions. However, the collisions require the particles to hit each other at a certain velocity, and if this velocity if not reached then the reaction will just not happen. So, at the higher temperatures, more of the particles were travelling at a high enough speed to collide and react. At the lower temperatures it was more difficult for the particles to collide. Particle theory says that for a chemical reaction to occur, there must be a collision at a certain velocity and at a certain angle. Also, the factors that affect the rate of a reaction are the surface area of the solid reactant if there is a solid reactant, the concentration of the aqueous reactant, the presence of catalysts and temperature. In this experiment we were concentrating on temperature, and we were able to draw the conclusion that temperature does, in fact, affect the rate of a reaction, in that when the temperature is higher the reaction takes less time. At 20°C the reaction took a long time to occur. This was because there was not very much heat. Heat provides energy to the particles of reactants, and if there is not very much heat, the particles do not have very much energy. Because they do not have much energy they will not move around much, and will therefore not collide very often. Chemical reactions require a certain speed collision to react, and at this temperature very few of the particles collided, because of not moving around more due to lack of energy, because the heat was not very great. Between 35-55°C the rate of reaction rises very dramatically. I can tell this from my graph, as the line of best fit goes up very steeply. See graph 1.b At 60°c the rate of reaction is at its highest as my graph shows, the best fit line is rising almost vertically. My results and evidence support my prediction very well. They prove the fact that temperature does affect the rate of reaction. I also have the particle theory to support my prediction and conclusion. Evaluation. I believe that the method we used was very good because we had one person using the syringe to mix the liquids together, we had one person timing and one person recording the results and checking the temperatures. I think this was a very good method because it makes the experiment very fair because the results we obtained are more accurate and fair than if we had used a different person each time for each thing. Also, we took great care in making sure that the measurements were as accurate as they could have been. Another reason our results are good is that we took multiple recordings and found the average for them, giving a more accurate result for each temperature. We may have timed one of the results wrong because it was a lot different from the other results, this is called an anomaly and we discarded it as it would have made the average lower than it should be. It is quite difficult to judge properly the exact moment that the cross disappears. It is even more difficult for the higher temperatures, as you would have to have an extremely good reaction time to stop the stopwatch exactly when the cross changes. However, our results were consistent. Although we did have one anomaly we made sure that the results were as accurate as they could have been. Concerning the amount of time taken for the cross to disappear, we could use a different method of working out how long the reaction took to occur. For example, we could shine a torch through the conical flask, and as soon as the light cannot shine through any more, we would stop the stopwatch. This would be one of the things I'd change if I did the experiment again in the future. For further work to our experiment, we could perform the experiment in a vacuum, as then there would be no other factors that can affect our results, other than temperature, which is the variable we wanted.   

My aim is to find out whether temperature has an effect on a rate of the reaction. I am going to be using the example of the reaction between Sodium Thiosulphate and Hydrochloric Acid. Prediction I predict that the higher the temperature, the more quickly the...

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When a car is... When a car is situated at the top of ramp, we say it has gravitational potential energy. When the car travels down the ramp, the gravitational potential energy is transferred to kinetic energy; so therefore KE= ½mv2 Kinetic Energy = ½ x mass x velocity2 At the bottom of the ramp work has to be done in order to stop the car; so therefore Work Done = Braking Force x Braking Distance Also, this must be equivalent to the original energy of the car, which was gravitational potential. So, assuming no other loss of energy: Potential Energy = Kinetic Energy = Work Done Prediction I predict that the higher the ramp, the more Gravitational Potential Energy, therefore the more Kinetic Energy and as a result the car has a bigger Braking Distance. This is because the more Kinetic Energy the car has then the further the car will travel. In this experiment I am investigating how the kinetic energy of the car affects the braking distance of the car. Therefore, I need to undertake some Preliminary work to make a series of predicted braking distances. In order to do this, the braking force needs to be calculated. As we can measure mass with a balance, Braking Distance with a ruler and velocity/speed with a light gate, but I do not know the Breaking Force, therefore preliminary work is done to get the value for this. Here is the equation for Braking Force; BF= KE ÷ BD OR BF=½MV2÷ BD Preliminary Work Now, I am going to find the braking force. To get my results, I will use a ramp height of 15cm throughout my Preliminary work and the same car which has a mass of 0.103kg. I will let the car travel down the ramp ten times, each time I will take note of the speed m/s and Braking Distance remembering to measure at the back wheels of the car every time This will then give me the appropriate measurements for the above equation to calculate the braking force. Method 1 Set the height of the ramp 15cm 2 Set the light gate up and link it to the computer 3 Weigh the Car record the mass 4 Load program 5 Roll the Car down the ramp ten times. 6 Each time record the results from the computer. This is the measurement of velocity/speed 7 As well as recording the braking distance. Here are my Results; Speed m/s Braking Distance m 1.03 1.50 1.13 1.31 1.07 1.465 1.15 1.45 1.10 1.495 1.14 1.52 0.96 1.31 1.14 1.665 1.10 1.35 1.17 1.635 Average = 1.099 Average = 1.47 Now I can calculate the braking force; BF = ½mv2÷BD So, BF = 0.5 x 0.103 x 1.0992 ÷ 1.47 BF = 0.062201751 ÷ 1.47 BF = 0.042314116 BF = 0.04 to 3.s.f. "“ this remains constant throughout my investigation. Prediction As I now know the braking force I can predict a series of braking distances, by using this equation; KE ½mv2 ÷ BF = BD Here are my predicted results; Speed m/s KE½mv2 Braking Force Predicted Breaking Distance 0.25 0.0032 0.04 0.08 0.5 0.0129 0.04 0.32 0.75 0.0290 0.04 0.73 1 0.0515 0.04 1.29 1.25 0.0805 0.04 2.01 1.5 0.1159 0.04 2.90 1.75 0.1577 0.04 3.94 2 0.206 0.04 5.15 2.25 0.2607 0.04 6.52   

When a car is situated at the top of ramp, we say it has gravitational potential energy. When the car travels down the ramp, the gravitational potential energy is transferred to kinetic energy; so therefore KE= ½mv2 Kinetic Energy = ½ x mass x velocity2 ...

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