### An Investigation To See How Resistance Can Be Changed By Variables

In order for the resistance to be changed I need to know the variables. To keep the current constant using an ammeter and variable resistor you will insure that you are not changing a constant. Copper wire will be used to link up the circuit this gives such little resistance that it is normally regarded as having no resistance. I think I will use size 24 wire as it is not to small and will not burn (giving an odd result) and not to big that so the resistance is not to high.

Three wires that are available are Copper, Nicrome and Constanton. The highest resistance should give me greater variance at the extremes so it is easier to record. In a pre-test I shall find out which wire has the highest resistance, before I decide which one to use.

The only problem with using the highest resistance is that if temperature is increased so will the resistances, so voltage will have to be low enough to not effect results.Variables;Wire Type- there are three types of wires Copper, Nicrome and Constanton. I will be using Constant as it gave the best range with out compromise of heat or length.Wire Length- the longer the wire the greater the resistance. I will be changing the variable wire length between a range.Cross Sectional Area- this is proportional to resistant and length so will not effect results.Current- this will be kept low so will not become hot, and effect resistance. A set value will be decided.

Temperature-the higher the temperature the wire is at the more resistant it becomes and will be cheap low enough not to let the temperature increase.Equtions;R = VI Resistance is equal to Voltage/CurrentR LC.S.ACircuit;Outline Plan;* The variable I will be changing is “length of Constanton wire.

“* I will find the length in a pre-test. I will also combine the to together to find out the range of length with the wire type.* I prepare the equipment setting out the circuit as shown and always making sure the amp. Meter reads 0.1 amps, to a nearest decimal place. To obtain this can be done by moving the variable amp.

Meter as it is making sure the content is constant as the resister is not a value if the amp. Meter reads 0.1amps.

* Check the wire for short circuits, turning on power if there is no wires touching.* Ensure voltage is low enough for the amp. Meter to read 0.1 amps.* Take results moving the length and repeating evaluate data collect any more data if there is any anomalous and needs checking out.

* Pack up equipment.* Analysis and the resulting data conclusion including graphs.* Evaluating data- showing strengths and weaknesses of the plan and data collected.Plan;To measure the distance of the wire, I will measure going in ten centimetres from ten to ninety. I will be using a meter stick and carefully stuck the wire to it. This insured that the same wire is used and measured in the same way if I have to collect data on anther day.* Step one- ensure power supply is not on when putting socket into switch.* Step two- set the wire and the measuring stick up using masking tape to attach it.

* Step three- set up the circuit making sure all the connections are together and no wire is crossing.* Step four- making sure power pack is on a low voltage and switched on take readings.* Step five- ensure meter is reading out 0.1 amps. when taking results make sue they are not silly or look out of place.* Step six- repeat steps before until all data is collected,* Step seven- look at the data for anomalies, if there are any repeat length, and discard odd data. Turn off power.* Step eight- pack up equipment putting it back into the right place.

Making sure no wires are burn or damaged.Remember: the electrical current or voltage is low coming out of the power pack but this does not mean that you can not get an electrical shock.Pre-test;We set the experiment as if it was the true experiment but only took the reading for the wires at the extremes, this would identify the range between. This would help me decide if the length of wire was also a good length to chose or if it need to be changed accordingly as well as the wire type.Constanton 24 swglengthAmps.Voltage1 meter0.10.

4710 centimetres0.120.04Copper 24 swg1 meter0.130.

0210 centimetres0.130.12Nicrome 24 swg1 meter0.120.6610 centimetres0.140.

13The range I have chose seems to give me enough variance between the two extremes for Constanton and Nicrome. I think I will use Constanton wire as it gave me a good range without exceeding the current that will be kept constant.Measurements and Observations;I will be measuring using a led screen with a digital out put to record my results with this will round up some figures but the rounding up will be so minor it hopefully should not effect the results.

The relationship between swg and mm in the size of diameter can be found in the table. The size I will use is 24 or 0.56 mm. I will have to look out for gaps in my circuit because if the circuit is not complete the reading will become very high and not change, this would give me odd results and would have to be corrected in order to keep all the data consistent.Here is a table of variables and the value they will be; (next to this table there will be anther table on relationship between swg and mm for diameter of the wire)VariablesValuesWire TypeConstantonWire LengthVaries, as it is the value testing.The range will be between 10 cm to 90cmC.

S.AThis will be kept at 24swg or 0.56mmCurrent0.1 to 2 decimal placesTemperatureThe wire should not heat up with the lowcurrent so will not be a factorSize in swgDiameter in mm200.9240.56280.4320.28360.

2This is the table of variables all these will be carried out in the experiment to insure it is a fair and even test.Equipment;The equipment needed for this experiment is;* Power pack- to insure there is a low current.* Variable Resistor- for fine-tuning of the current so is stays the same.* Wires- linking the circuit together made from copper.* Crocodile clips- to go on the end of the wires to attach them selves firmly to the wire.* Meter ruler- so measurements are accurate the wire will be stuck onto the stick so no stretching or weakness occurs when taking results.* Masking tape- to attach the wire onto the ruler making sure you can reach the wire you are connecting the stick.

* Voltage meter measures the output data. (make sure this in parallel to the circuit or all the readings will be the same)* Amp. Meter- to insure impute data is all of the same current level.Readings and number of readings;I will be taking around three result for each lengths of the wire however if there is an anomalies the whole lengths for that go will be redone to make sure the readings are correct. The suspected anomalies are going to be any data that goes to far from the other collected data and may change the figure when rounding later in the analysis. The data will be collected to 2 decimal places as the reading on the voltage meter and ammeter will only go that far with in a sensible boundary.

This means however it might have some influence on the results, a more accurate way is needed with more figures and the digital output longer.Prediction;The resistance of wire should depend on the variable chosen to control but the length. When electrons travel through the wire they will collide with particles slowing the electron down. When they collide they use energy up and the voltage increases, as more energy is required to make the electrons move. This should means the longer the piece of wire the more collisions that will that place during the circuit. When the wire is short but thick in diameter the electrons will travel through using up less energy and colliding less, as they all travel through the distance and get through quicker. This means if you have a long thin, wire the resistance is high as they have more distance to travel so more opportunities for the electrons to collide.

The diameter is then proportional to the length with resistance. This shows that wire does have a variance and is dependant on the wire chosen. As the diameter is the same the distance shall only matter. I predict if the electrons collide once in ten centimetres they should roughly collide twice every twenty centimetres. This should give me a straight line when drawing a graph. The gradient of this line will be determined by the amount if resistance intentionally of the wire, and will stay constant al the way through giving a straight line of best fit.Obtaining Evidence;To see if the data I collected had any patterns or similarities I put in a data so it would be easily processed and easy to note down the values while doing the experiment.

Here is the data collected;Results;Lengths of Constanton wire in cm to 1 d.p.Voltage Output in Volts to 2d.p.Average VoltageThe range of the readings 10cm to 90cm.(V)in volts to d.p (V)100.

070.040.040.040.04200.090.

090.090.090.09300.130.140.130.140.

14400.180.190.

180.190.19500.

240.230.230.

230.23600.270.

290.270.270.28700.310.

360.320.320.

32800.370.380.370.360.37900.40.430.

410.410.42With the data collected it can now be processed the average is the process that rounds of the figures so they are closer, and more accurate. The resistance is worked out so a graph can be drawn this helps me see if the data has a relationship (straight or cured line) and to see if any anomalies are present or figures that do not quite fit the others when a best fit line goes throughout them. The best-fit line is there not joining all the points unless they have a certain relationship followed through out the whole data, is there is no relationship the graph will not have a best fit line but will join up the points, only on a line graph.Analysis Evidence and Drawing Conclusion;Lengths of Constanton wire in cm to 1 d.p.

Ohms resistance in ohms(?)The range of the readings 10cm to 90cm.100.4200.9301.4401.9502.

3602.8703.2803.7904.2The real value of the wire can be found out the real value for Constanton is 4.7? for a meter if I take 50cm as an example the 4.7? would be divided into 2 as 50cm is half that of a meter.

The true result should have been 2.35? the result I found was 0.05? of this point.

This could be explained by the rounding of some figure but it is so close I believe my experiment was well executed as it almost gained the true value. This would be the best I could have hoped for using the limited decimal places by the digital read out.(See graph of result and notice the straight line of best fit showing a define relationship)Conclusion;The data I collected make it possible to simulate and work our calculations producing a graph with line of best fit. The data could be used for working out the resistance per meter of wire, and the average of the results that it needed in order to be worked out. With this data I plotted a graph, it was straight and has a best line going almost all trough the points. The prediction estimated that the data would produce a straight line on the graph and would be the same gradient. The data drawnshows this and showed that the prediction was in the right area of view. The prediction did not estimate the gradient of the line this was almost impossible from the initial data collected.

The results could curve if the prediction was not correct and if it did it would be difficult to estimate this, this would only be viewed on a graph so all the data would have to been collected to see the results. The line does not goes exactly go through all the points as some margin of error is always expected, but the are very close to the line. If the true value is worked out for fifty centimetres it is only 0.05? out of the value which has been recorded in perfect laboratory conditions and with higher accuracy measuring machines than for two decimal places.

The true value of the wire is 4.7? for the meter and when 2.35? for fifty centimetres, the value I reached was 2.3?. This is very close and could be accounted for rounding of values on the digital output of only two decimal places.

Evaluating Evidence;The data collected was collected in the same way and with the same instruments. It is very close to the real value and I believe it is a good indication that when the length of the wire is increased the resistance does as well in almost set values for different wires. This would give a straight line on the graph that was produced when the data collected was plotted. The only slight waver in the result when the had be processed was the data for the length 0.7 meters, this is so slight how ever that it is of no worry as it still is clearly next to the line and is following the pattern but with slight irregularity. The length was chosen to be in the middle value of 24 swg so it would not heat up and make the resistance even higher.

This chose the gradient of the line as it was propitiation the resistance and is the mains other factor in the wire that may have determined what the results would be. The equipment there was no problems with the working order but there was in the limitation of the two decimal places on the out put screen. The other explanation for this is that the current was changing and be corrected to 0.

1 amps, this was done but with the limited display could not see how far away the value was. If it was lower it would give a slightly lower result with no indications through the method suggested or show up until all the result have been sorted and calculations made on the data.The other difficulty I can think about would be the movement of the wire and the crocodile clip, if it were not placed exactly on the same length each time the display may flicker and add a value on or way.

The data collected was also taken from the digital out put however this out put was changing or flicking from different values. It was taken on my discretion, the result I chose was that which it seemed to stay on the most or the highest value if roughly the same.Information collected in this experiment could be compared with data of other resistance of wires to see if the resistance or gradient of the line if graphs were drawn, was the same or if it was completely random from metal to metal.

This would help decide how resistant the wire becomes and if extended the length and it discontinuation or continued. The other interesting things to continue with the experiment would be the connection of other alloys and their relationship with themselves, and heavier and lighter alloys of the same type.The data collected and compared would then be used to see how effective the alloy is at resistance and how far this resistance extents till it is all off one metal or the other. This extra work would make sure the length is constant for all wires, also comparing with alloys and their effect on the gradient would be noted on how much the compound changes the resistance. This work would make the information gather from this experiment valid and help find out the effect on changing the concentration of metals.The experiment followed the original prediction and with only a slight waver with length 0.7 meters the true vale was almost completely correct and could only be made clearer of error if more accurate measurement equipment was available.