To investigate whether or not the length of a piece of a wire affects the resistance Background Information Resistance is a measure of how difficult it is for a current to flow in a circuit. It is measured in Ohms. The higher the resistance the lower the current. Ohm’s Law is all about resistance. It is: I = V/R. So to work out resistance the equation is R = V/I. Preliminary I plan to investigate how the resistance of a 32 swag nichrome wire is affected when i change the length of the wire that is used in the experiment. Length of Wire (cm) Current (A) Voltage (V) Calculation.
Resistance Wire at 10cm 1Wire at 20cm Wire at 30cm When I did the preliminary I did not use a variable resistor. In order to get accurate results I must keep my current the same at every length. To do this I can use a variable resistor. By adjusting the settings on a resistor once it is placed in my circuit, I can keep the current the same at every length that I try. This means that I can be more confident in my results because I will know that the differing current will not affect my resistance.
Also, in order to get a more varied range and more reliable results I will go from 10cm of wire to 50cm. Equipment Lead x6 Crocodile Clips x2 Variable Resistor x1 Metre Ruler x1 Power Pack x1 1m Nichrome wire – 32 swag x1 Ammeter x1 Voltmeter x1 Calculator x1 Cello-tape x1 Lead – To create the circuit with and to keep it complete in order to carry out the experiment. Crocodile Clips – To attach the leads to the nichrome wire and allow the circuit to be complete. Variable Resistor – To control the current and keep it the same at every length in order to make my experiment a fair test.
Nichrome 32 swag wire – This is the wire I am testing the resistance of. Metre Ruler – This is used to keep the nichrome straight and to measure the length of the wire. Power Pack – This is my power supply. Without it the circuit would not work. Ammeter – This is used to measure my current. Voltmeter – This is used to measure my voltage. Calculator – I will use this to do the calculations and work out my resistance using Ohm’s Law. Cello-tape – I will use this to secure my nichrome wire to the 1m ruler in order to keep it straight. Main Experiment Diagram of Circuit Results Tables Nichrome Wire Sample 1 Sample 2
Sample 3 Length (cm) Current (A) Voltage (V) Resistance () Current (A) Voltage (V) Resistance () Current (C) Voltage(V) Resistance () Outliers Method 1. Set up the circuit making sure that all the apparatus is in the correct place. 2. Set the wire to 10cm. 3. Take a measurement of the current and voltage using the voltmeter and ammeter.
4. Use the variable resistor to make sure the current stays constant at 0. 21A. 5. Divide the voltage by the current to get the resistance and write down the result. 6. Set the wire at 20cm, 30cm, 40cm and 50cm and repeats steps 4, 5 and 6. 7. Repeat the whole process 3 times to ensure degree of reliability in your results. Variables In order to make sure that my experiment works, I must have a number of variables. The first of these is my voltage. I am leaving this as it is and leaving it to change according to the length of the wire. This is because voltage is directly linked to the amount of resistance.
This is an independent variable. An independent variable is a variable that I will let change by itself. This is the opposite of a dependent variable. A dependent variable is something that will remain the same throughout my whole experiment e. g. the current. The second variable is also independent. This was the length of the wire. In order for my experiment to work then the length of the wire must be changed and thus, it is an independent variable. Conclusion Using the results of my experiment, I can confidently say that, as the length of the wire increases, the resistance also increases.
I can tell this because; on my graph and in my results there is a constant positive correlation. This is because the longer the wire is, the more collisions there are between atoms and electrons, and therefore, there is a larger resistance. However I cannot be completely confident in my results as I did have to discount two results when I calculated my averages. Evaluation During the actual experiment there were a few things that could have gone better. One of these was the actual measuring of the nichrome wire. To measure it accurately and keep it straight I had to attach it to a metre ruler.
Because of the way it had been stored, the wire would never be completely straight and had several kinks in it. This could have caused slight inaccuracies in my results. This could be rectified by using a newly bought wire so that it will be completely straight and will not affect my results. Also I had to use a voltmeter and an ammeter to work out the resistance. Because of the process of the actual calculation there likely to be things like the rounding of numbers that can slightly change the results and affect the reliability of the whole experiment.
In order to make my resistance more accurate I could have used an ohmmeter rather than a voltmeter and an ammeter. I can tell that my results are fairly reliable because, on my graph, my line of best fit falls in between all but one of the error bars. However I cannot be totally sure of my results as two of my results had to be discounted. This was because they were drastically different to the other results in that sample. These outliers could have been caused by a slight error in measuring out the wire or by an error when setting the variable resistor to keep the current constant.
This could have caused a fluctuating current. These problems can be resolved by checking everything before I take any readings. One thing I could have to done to improve the reliability of my results was to do more repeats. If I had more readings then my averages would become more reliable. However I feel that with the amount of repeats that I took I can be, overall, fairly confident in my results. Show preview only The above preview is unformatted text This student written piece of work is one of many that can be found in our GCSE Electricity and Magnetism section.