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Experiment on Resistance - different lengths of wire.

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SCIENCE: INVESTIGATION INTO RESISTANCE Electricity in general Resistance is anything in a circuit which slows down the flow of a current. It can be caused by collisions of the electrons into the material's atoms. The current is the flow of electrons in a wire, and it is literally pushed around the circuit with the help of the force of Voltage (which is generally the pressure difference in a circuit). The resistance opposes the amount of voltage and stops the currents from flowing properly. The amount of current flowing through a circuit is directly proportional to the amount of Voltage or resistance is in the circuit; the current will flow faster with high Voltage and low Resistance as opposed to low Voltage and high Resistance, which would make the current flow slower. The electrons in metals carry the current, and each metal has a "sea of electrons" which can move around easily, so the current can pass on. Metals have so many electrons as since all of the electrons on the outer shell of the atoms release their electrons, which hold the atoms together in a metallic bond. These electrons are now free to move, and with their negative charge they carry the current. ...read more.


Semiconductor Diode A diode is made from a semiconductor material (material which conducts less compared to other metals). It stops current going in one direction (making it a direct current). LED (Light Emitting Diode) Another diode, so it only allows current to flow in one direction. An advantage of it is that lights are given out when a current passes through it, so you can see when something is actually working or not. LDR (Light Dependant Resistor) This resistor reacts on light; when light is present, the resistance falls, and when there is no light the resistance rises in the circuit. It's useful for automatic night lights, which would turn on when the change of light occurs. Temperature-Dependant Resistor It works similar to the LDR, but this one allows higher resistance in cooler conditions and less resistance in warm conditions. This is good for when trying to keep something at a constant temperature - all you would need to do is see the change of a light bulb in a circuit with this resistor to see if the temperatures either increased or decreased. EXPERIMENT ON RESISTANCE - DIFFERENT LENGTHS OF WIRE V C (1a) ...read more.


Evaluation The results, however, are not accurate. The 12cm variable resistor setting did not give us a proper reading on the ammeter and voltammeter, and so we had to change the setting on the power pack from 1 ampere to 5 amperes. Otherwise, the experiment went very well, as we got all of our results as accurately as we possibly could. We got a few 'freak results,' as you can see at resistor setting 6cm and wire lengths 45cm and 50cm, where the resistance has dropped quite a lot compared to resistor setting 3cm and wire lengths 45cm and 50cm. I am not sure how this was obtained, seeing as the resistor setting had increased so the resistance should have as well. It may be that one of the items was not measured accurately. To improve on my experiment, next time I would definitely make sure that all the power packs and ammeters/voltammeters are set to 5a, so that none will be different. Also, I would use digital ammeters/voltammeters, as they would be more accurate - the needles in the analogue ones can be shook and moved about, giving an inaccurate reading. I would also need to work on a method for giving 100% accurate measuring. To expand on the experiment even further than this, I could involve different widths of wire as well. ...read more.

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