Two Readings For The Same Wire Length example essay topic

IF YOU INCREASE THE VOLTAGE - MORE CURRENT WILL FLOW. IF YOU INCREASE THE RESISTANCE - LESS CURRENT WILL FLOW (UNLESS YOU INCREASE THE VOLTAGE). ' 'o'In Metals The Current Is Carried By Electrons 1. Electric current will only flow if there are charges, which can freely move. 2.

Metals contain a sea of 'Free Electrons' (which are negatively charged). And flow throughout the metal if they are given energy. 3. This is what allows electric current to flow so well in materials. ' 'o'Resistance Resistance is anything that causes an opposition to the flow of electricity in a circuit. It is used to control the amount of voltage and / or amperage in a circuit.

Everything in a circuit causes a resistance (even wire). It is measured in OHMS ( ). Resistance occurs when the electrons travelling along the wire collide with the atoms of the wire. These collisions slow down the flow of electrons causing resistance. Resistance is a measure of how hard it is to move the electrons through the wire. The resistance of a wire depends on the number of collisions the electrons have with the atoms there will a larger number of collisions which will increase the resistance of the wire.

If a length of a wire contains a certain number of atoms, when that length is increased the number of atoms will also increase. e.g. If there is a wire that is half the length of another wire it would also have half the number of atoms, this means that the electrons will collide with the atoms half the amount of times. Also if the length of the wire is trebled or quadrupled then the resistance would also treble or quadrupled. ' My prediction was derived from this information. All of this information I collected originated from the Website, ' web ' from encyclopaedias such as 'The Oxford Children's Encyclopaedia' and computer encyclopaedias such as 'Encarta'. 'this scientific information relates to my experiment by stating that the longer the lengths of wire the higher the resistance. 'preliminary Results Length Of Wire (mm): Voltage (V): Current (A): Resistance ( ): 'therefore this information supports my prediction that the longer the length of wire the higher the resistance. Obtaining Evidence: 'o The variables I kept the same are: ^o The same material used for the wire, ^o The same cross-sectional area of wire, ^and the same temperature of the wire. 'o The potential difference from the power pack: 2 V. 'o The current, which measured the rheostat, was kept at: 0.5 A. 'o The lengths of the copper wire: If the diameter of the wire was wider then more electrons could get through therefore less resistance. So the thicker the wire the lower the resistance because there is a bigger area for the electrons to travel through, so there will be less chance of them colliding into one another which means there will be less energy produced.

I predict the longer the wire the higher the resistance and the shorter wire the lower the resistance. I think this because the longer the piece of wire the further the electrons have to flow, then that would mean the more collisions with atoms, which would increase the energy therefore increasing the resistance. Also if I double the length then I double the resistance. The electrons start of with kinetic energy they then collide with other electrons, which is then transferred to heat energy. I think that the shorter the wire the lower the resistance because they have less of a way to travel which means they wont collide with as much atoms, therefore less energy will be produced.

Background Info: Resistance opposes the flow of an electric current around a circuit so that energy is required to push the charged particles around the circuit. The circuit itself can resist the flow of particles if the wires are either very thin or very long. e.g. The filament of an electric light bulb. Record this reading on your table. The table should have a space for Length and Current. 5.

Now shorten the length of the wire slightly by changing the position of the crocodile clips, maintain the voltage using the variable resistor, and jot down your reading from the ammeter. This procedure should be repeated until you reach the minimum length. (The minimum length will be discussed in the preliminary section later on). To ensure that obtain a good quality of results this experiment needs to be fair.

Since it is the length of the wire that we are essentially investigating, this is the only factor that should be changed during the investigation. All other variables shouldn't change. If possible all the results should be taken in one lesson as you can guarantee that the same equipment will be used. The component must remain the same throughout the investigation as should all the other equipment. An important factor that needs to be controlled is the temperature. As we know a higher temperature means a greater current.

Continuous variations in temperature will have the consequence of inaccurate results and in the long run may not be sufficient enough to support my prediction. The aim is to obtain reliable evidence that supports my prediction and enables me to draw a conclusion from. A way of managing the temperature is outlined in the preliminary section. To ensure greater accuracy it will be necessary to repeat the experiment. That is, I will take two sets of readings. To ensure consistency and accuracy across the whole investigation I need to decide on the range of values to take.

The maximum length of wire to use is 1 metre. I decided that readings of 10 different lengths should be sufficient enough to produce a pattern and also a curve for graphs in the Analysing and considering evidence (A) section of the coursework. I have done some earlier work in order to help this planning. This is called the preliminary or initial work. The aim of doing preliminary testing is to: find out the most suitable conditions that can be used to do this investigation. Be completely straight during the experiment, to avoid short circuits.

Bends and kinks in the wire could also affect the resistance. o The voltage reading must be taken as soon as the circuit is connected. This will minima lise the current's effect on the temperature of the wire and thus the resistance. Reliability o each reading will be taken twice. Then both readings will be averaged to give the voltage. If two readings for the same wire length are very disparate, further readings will be taken to insure an accurate result. o To make the experiment reliable, all apparatus must be checked to see if it is functioning properly and is giving a true reading. o We will use the same apparatus throughout the experiment to make sure that nothing changes. o We will have the lengths all 5 cm apart so that the results are not too similar and so it will be reliable. I observed that the wire got hot when I was constantly using it.

This could have affected the resistance a bit, as when the wire is hot the electrons in it are already moving very fast as they have a lot of energy. This would have made the resistance more then it should be, as the atoms are moving fast. Conclusion: From my results I can tell that the length is proportional to resistance, they go up by approximately the same intervals each time. This is what I predicted, as you increase the length, the resistance will also go up. They are proportional as, if you increase the length, e.g. 5 cm to 10 cm, the resistance goes up proportionally, 0.36 to 0.49 Ohms. This is because the current has more material to go through, and so it is harder to get through.

This is the resistance getting bigger. This is because the longer the wire, the further the current has to travel, so it will have more resistance then if it were a shorter wire. It will have more pushing against the flow of electrons, and so it will have more resistance.