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Investigating how the length of a wire Effects resistance.

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Introduction

Lee Powell Investigating how the length of a wire Effects resistance. Planning Aim: I am going to investigate how the length of a wire affects resistance. Scientific Research: Current is a flow of charged particles, usually through a circuit, in all dry conductors, the flow is of electrons and so are negatively charged. Resistance is in electricity, it is a property of an electric circuit or part of a circuit that transforms electric energy into heat energy in opposing electric current. Resistance involves collisions of the current-carrying charged particles with fixed particles that make up the structure of the conductors. Resistance is often considered as localised in such devices as lamps, heaters, and resistors, although it is characteristic of every part of a circuit, including connecting wires and electric transmission lines. Resistance has a relationship with length, the longer the length of the wire the greater the resistance. This is because there are more positively charged particles to get in the way of and collide with the electrons. This means there are more particles to get past so the resistance is increased. There are four factors that can affect resistance, varying cross sectional area of the wire, different material for wire, temperature of wire, and the one I am interested, in varying length of the wire. ...read more.

Middle

Apparatus Diagram: Method: 1. collect equipment. 2. set up equipment, as shown in apparatus diagram. 3. use metre ruler to measure 50cm of wire, and attach crocodile clips. 4. switch on, use variable resistor to get 1v on voltmeter. 5. record reading from ammeter, then switch off to let the wire cool down. 6. repeat steps 4 and 5 for 2V, 3V, 4V and 5V. 7. repeat steps 4, 5, and 6 for lengths 60cm, 70cm, 80cm, 90cm, and 100cm. Fair Testing: * To make sure the test was a fair one, we had to make sure the wire was the correct length, measured very accuratly. * We had to try and keep the temperature as constant as possible, this would mean allowing the wire to cool down after each test. Results: length=50cm voltage(V) current(A) Resistance(?) 1 0.41 2.44 2 0.83 2.41 3 1.24 2.42 4 1.65 2.42 5 2.1 2.39 average resistance=2.42? length=60cm 1 0.35 2.86 2 0.7 2.86 3 1.05 2.86 4 1.39 2.88 5 1.73 2.89 average resistance=2.87? length=70cm 1 0.28 3.57 2 0.57 3.51 3 0.85 3.53 4 1.13 3.54 5 1.4 3.57 average resistance=3.66? length=80cm 1 0.27 3.7 2 0.53 3.77 3 0.81 3.7 4 1.08 3.7 5 1.35 3.7 average resistance=3.71? ...read more.

Conclusion

This means our experiment was conducted well. The experiment just about followed Ohm's Law, the reason it didn't quite follow Ohm's Law absolutely is because Ohm's Law is only correct if the temperature remains the same. My experiment followed expected results as can be seen by using my prediction, results tables and graphs. I have a few anomalous results, the most obvious one is on the "A graph to show average resistance against length" it is at 70cm, most of the other results are very close to the lines drawn on the graphs so must be quite accurate. The reason I have these anomalous results is due to change in temperature while completing the experiment. I believe that I have gathered enough evidence to support my conclusion, I repeated the experiment five times for each different length to make sure of this, and get an accurate average resistance. Improvements: * Some improvements I could have made are to have kept the temperature constant, and made shure of this, by keeping the length of wire in a water bath at a constant temperature. * I could also have made the experimient contain more values, e.g. go from 1-10V instead of 1-5V this would mean I would get more results, and the average result would have been more accurate, as the anomolies wouldn't affect the results as much. * * * * ...read more.

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