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The Resistance of a Wire

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Introduction

The Resistance of a Wire Prediction Aim The aim of this experiment will be to determine the relationships the physical characteristics of constantan have with its resistance. Before this, the variables in the experiment need to be defined which ones can be changed and which should remain the same. Dependent Variables Current- Measured in amperes or amps. I=V/R Current is a dependent variable that will be changed. Resistance- Measured in ohms. R=V/I Voltage- Measured in volts symbol V, V=IR Independent Variables Wire length- the length of the wire is a physical characteristic independent of any other variable does not effect. Therefore, at least one physical characteristic must be changed. Density will remain constant because constantan will always be used, so length would seem a good physical characteristic to vary- i.e. for each length of wire a reading will be taken for a range of potential differences and then another length of wire will be used. A very simple experiment proves that resistance is directly proportional to wire length- when one light bulb was placed in a circuit and the voltage across and current through recorded, thereby allowing its resistance to be calculated, another was placed in series with it, which doubled the resistance. In equation this is- R=KL Where K is some constant and L is length. ...read more.

Middle

To ensure a fair test, the same piece of wire will be used for each set of readings, but crocodile clips will be placed on it at the appropriate point o incorporate the correct length into the circuit. Apparatus Multi-meter- set to 200-ohm range, allowing readings in this range to be taken accurately. Due to the miniscule amount of current flowing from the multimeter, temperature change in the wire will be negligible, so readings for lengths as low as 10cm can be taken, unlike in the main experiment. Connecting wires- as short as possible to ensure the resistance added by them to that of the constantan is as low as possible. Crocodile clips- ensure these are in as good a condition as possible. Also ensure that the Constantan is placed right at the tip of each, to minimise resistance from them. Constantan- Standard Wire Gauge of 26. Greater than or equal to 120 cm in length, allowing lengths in 10cm increments up to this length. This will also allow a reading for 100 cm to be taken. Method 1-Place the crocodile clips connecting the wires to the constantan as close together as possible on the constantan. This will effectively give the constantan a length of zero, meaning that any resistance recorded will be that of the connecting wires themselves. ...read more.

Conclusion

Resistance in ohms (Corrected) 0 0.2 0 10 0.5 0.3 20 0.8 0.5 30 1.1 0.9 40 1.4 1.2 50 1.7 1.5 60 2 1.8 70 2.3 2.1 80 2.6 2.4 90 2.9 2.7 100 3.2 3 110 3.5 3.3 120 3.8 3.5 Main Experiment Current (Amps) Resistance (Ohms) Length (cm) Voltage (Volts) Set 1 Set 2 Average Average 60 1 0.6 0.58 0.55 1.818 60 2 1.16 1.18 1.17 1.709 60 3 1.74 1.66 1.7 1.765 60 4 2.36 2.33 2.345 1.706 60 5 3 2.93 2.965 1.686 60 6 3.6 3.4 3.2 1.875 1.76 80 1 0.4 0.35 0.375 2.667 80 2 0.83 0.77 0.8 2.5 80 3 1.28 1.24 1.26 2.38 80 4 1.7 1.65 1.675 2.388 80 5 2.16 2.07 2.115 2.364 80 6 2.63 2.59 2.61 2.299 2.433 100 1 0.34 0.36 0.35 2.857 100 2 0.67 0.68 0.675 2.963 100 3 1 1 1 3 100 4 1.35 1.38 1.365 2.93 100 5 1.68 1.7 1.69 2.959 100 6 2.05 2.1 2.03 2.956 2.944 120 1 0.3 0.3 0.3 3.334 120 2 0.55 0.57 0.56 3.571 120 3 0.8 0.86 0.83 3.614 120 4 1.1 1.15 1.125 3.556 120 5 1.4 1.43 1.415 3.38 120 6 1.7 1.74 1.72 3.488 3.49 140 1 0.25 0.25 0.25 4 140 2 0.5 0.49 0.495 4.04 140 3 0.74 0.74 0.74 4.054 140 4 1 0.99 0.995 4.02 140 5 1.2 1.24 1.22 4.098 140 6 1.5 1.5 1.5 4 4.035 10 1 ...read more.

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