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To investigate the resistance of different materials in the form of wirer, resistors and other materials.

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Introduction

Ohms Law Planning A: Aim: To investigate the resistance of different materials in the form of wirer, resistors and other materials. Hypothesis: The shape, the thickness, the length of the resistor and the material that makes up the resistor itself will affect the electric conduction capability (resistance). Electrons can create a current, so the more free electrons there are, the more conducting capability that material has that is why metals conduct. Materials with wider diameter have more free electrons because the surface area is bigger compared to length so more electrons are free per cm as example. So if a cable is bigger in diameter it should have less resistance. Resistance will also increase as the length of the wire increases because electrons will be slowed down while traveling. ...read more.

Middle

* Resistor Method: * Connect the wires to the circuit by the crocodile clips * Take the voltage and current readings from the meters * Increase/decrease the supply from the power pack and take the readings again * Repeat the experiment with different materials, wires, bulbs, resistors Results: Wire: Setting Volt Actual Volt Ampere Milliampere Resistance Ohms 2,00 1,80 0,100 100,00 18,00 4,00 3,50 0,200 200,00 17,50 6,00 5,50 0,300 300,00 18,33 8,00 7,50 0,420 420,00 17,86 10,00 9,30 0,520 520,00 17,88 12,00 11,40 0,600 600,00 19,00 Average: 18,10 ? Bulb (variable resistor used): Actual V Ampere Milliampere Resistance Ohms 1,40 0,12 120,00 11,67 1,70 0,14 140,00 12,14 1,80 0,14 140,00 12,86 2,60 0,15 150,00 17,33 3,50 0,16 160,00 21,88 4,40 0,18 180,00 24,44 5,50 0,28 280,00 19,64 7,50 0,32 320,00 23,44 Average: 17,92? ...read more.

Conclusion

Here the current and voltage are not proportional. The bulb obviously gets hotter and hotter. Since "resistance" is measured by the gradient of the graph, we have here an example where the resistance is increasing. But obviously we are dealing with "normal" resistors in this investigation, so the gradient of the graphs obtained should be the same throughout linear and the resistance should remain constant as the voltage/current is changed. Evaluation: * To get better results the following things should be done: * The power supply should be varied smoothly between 0-12V with 0.1V interval so more averaged results can be taken. * Temperature has to be absolute constant to create a fair test. Otherwise Ohms law will not apply. * Better quality equipments should be used. * More accurate Meters Philipp C. Protschka Page 1 of 6 1 May 2007 Physics Practical Last printed 12/3/2002 12:16 AM ...read more.

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