Length Of The Wire In My Experiment example essay topic

Aim: My aim in this experiment is to investigate how the electrical resistance of a wire is affected in relationship to the length of that wire Factors affecting resistance these include: . Diameter or thickness of wire. Temperature at which wire is kept. The material from which the wire is made... The length of the wire In my experiment I will only be investigating one factor which is the length of the wire. The wire I am using is made out of nichrome.

Background information: Resistance controls the amount of current flowing through a particular component in a circuit. Resistance slows down the current. Current is defined as the rate of flow of electrons through a circuit current is measured in amps. A circuit can only possess a current if there is a voltage across a component.

The voltage is the force that is exerted onto the electrons to allow them to flow through the circuit. In 1826 a German physicist called George Ohm discovered a new rule which said that for a given conductor at a fixed temperature voltage is directly proportional to current. This relationship is better known as Ohms law. Ohms law also shows that resistance can be calculated using the following formula: Resistance = Potential difference / Current Resistance occurs when a large amount of electrons are pushed through a conductor and so they collide with positive ions in the lattice. When they collide they lose energy which slows them down. This energy is picked up by the ions this results in a reduced current and a increase in temperature.

Hypothesis: 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: Resistance Length I think this because (as I have briefly explained in the introduction) 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.

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. 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 resistively of the wire, in ohm-meters (~n) 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 length. Equipment required: Ammeter Voltmeter 6 connecting wires 2 crocodile clips Variable resistor Power pack 100 cm wire (Nichrome) Board (to place under the wire to prevent burning of table. Setting up the equipment: 0 100 Risk assessment: Safety plays a fundamental role in any experiment so it is very essential that it be carefully considered. There are a few main safety hazards that need to be addressed for example it is unsafe to leave the power pack on after you have done your experiment because prolonged sessions of the power pack being on result in a increased temperature of the wire.

The wire becomes very hot and can scold an individual if it comes in contact with the skin. Therefore it is essential not to leave the power pack running for long periods of time. Another thing is that the wire being hot could mean that it burn materials it comes in contact with such as a lead etc. This is very dangerous. This is why it is important to put a board underneath the wire so that it does not burn the table and also not to touch the wire whilst it is hot. In addition to this there is the general things such as equipment which may be dangerous such as the crocodile clips where someone's fingers could get trapped or the variable resistor which could trap someone's hair or a power pack falling and breaking someone's toes.

SAFETY COMES FIRST. Fairness: Fairness means the difference between the right results and the wrong results. So it is again vital to include it. In order to make this experiment fair the other factors that affect resistance will need to be kept the same.

Meaning that the temperature will need to be controlled this can be done by letting the wire cool down after each individual test so that it does not heat up too much. Also the wire I use should be maintained throughout the course of the experiment. If I use a different wire there is a risk that it will be slightly different even if it is the same type of wire. If the tests are fair then the results wont be manipulated in any way and therefore accurate results will be obtained. Method: I will begin by setting up the equipment as shown above. After doing this I will use the variable resistor to adjust the ammeter reading to 0.2 amps.

Then I will place my crocodile clips 100 cm apart on the wire after doing this I will take the voltmeter reading. After taking each reading I must remember to turn the power pack off before I change the situation of the circuit. Then I will change the length of the wire to 90 cm from I will not change the current and I will take the voltmeter reading I will repeat this with a 80, 70, 60, 50, 40, 30, 20, and 10 cm length of wire and take the voltmeter reading for each. After doing this will move the variable resistor so that the ammeter reads 0.4 amps again I will take the voltmeter readings for the 10 different lengths of wire. Then I will change the current to 0.6 and repeat the experiments with the 10 different lengths of wire. After I have done all the experiments with the different ammeter readings and the different lengths of wire I will then place all my results on a table of results.

From his table of results I will work out the average results of the resistance for each length of wire. I will then plot a graph showing average resistance against length. This graph should help me come to a sensible conclusion. Table of results: The table shows that as the length decreases the voltage decreases and the resistance increases. Graph to show the relation ship between length of the wire and resistance. Conclusion The results I have gained from my experiment agrees with my prediction that as the length of the wire increase then so to will the resistance of that wire.

The table shows that the resistance decreases with the length of the wire. Although the points on my graph do not form a straight line my best-fit line (being straight and through the origin) suggests that the resistance is proportional to the length. However I can see from my graph that there are a few points which do not fit the regular pattern off the graph. There are two in particular, which are straying off the path that the other points have created (60 cm and 70 cm) however this inaccuracy is minimal and despite it the outcome of the experiment is still as it was expected. The graph is still reliable enough to allow me to come to a reasonable conclusion. I can confidently conclude that resistance is directly proportional to the length of the wire and I can back this up using the following scientific explanation: As the length of the wire increases the number of electrons moving through it increases.

The more the number of electrons in the wire the more "crowded" the piece of wire becomes. This causes an increase in the number of collisions between the moving electrons and the static-positive ions in the lattice. These collisions result in a decrease in the amount of energy carried by the electrons and the potential difference across the wire decreases. The resistance increases as a result of the voltage decreasing.

So if the length doubles the collisions double the resistance doubles. So therefore it is logical to assume that the resistance is directly proportional to the length. Evaluation: As I have pointed out in my conclusion there are a few anomalous results. Even though I have been able to conclude my investigation I feel it is still important to address these particular errors so that next time the same mistakes wont be made.

These errors could have occurred for one of many reasons in my opinion the most likely one would be that fact that the wire heated up and referring back to the sections stating factors which affect resistance it says that one of them is temperature. It is important to maintain the same temperature throughout the experiment or the results will be manipulated however it is hard to keep the temperature of the wire the same because heating up of the wire is inevitable once there is a current flowing through it. Another reason for the slightly dodgy results could be the fact that the equipment was not up to scratch the ammeter or the voltmeter may have been faulty this would have caused an error in my results. On the other hand it could have been an error made by me when taking down the readings or setting up the experiment. Any one of the above statements can be taken into consideration to decide what the cause of the errors was. All in all I think that my range of values was good because I was provided with a wide range of values to help me get a better - more all round perspective.

I if was to do the experiment over I think I would definitely include more reliable equipment such as digital meters etc. Other than that I was pretty much happy with the way I carried out my experiment I followed the risk assessment carefully and took the fairness factors into careful consideration. If I was to re do this I think I would find it interesting to maybe investigate the other issues that affect resistance such as the width of the wire or the material etc. I feel that I got what I was looking for in this experiment.