-->

Pages

Thursday, May 31, 2012

Resistance

If you order your custom term paper from our custom writing service you will receive a perfectly written assignment on Resistance. What we need from you is to provide us with your detailed paper instructions for our experienced writers to follow all of your specific writing requirements. Specify your order details, state the exact number of pages required and our custom writing professionals will deliver the best quality Resistance paper right on time.

Out staff of freelance writers includes over 120 experts proficient in Resistance, therefore you can rest assured that your assignment will be handled by only top rated specialists. Order your Resistance paper at affordable prices with livepaperhelp!



Theory


What is resistance?


Electricity is conducted through a conductor, in this case wire, by means of free electrons. The number of free electrons depends on the material and more free electrons means a better conductor, i.e. it has less resistance. For example, gold has more free electrons than iron and, as a result, it is a better conductor. The free electrons are given energy and as a result move and collide with neighbouring free electrons. This happens across the length of the wire and thus electricity is conducted. Resistance is the result of energy loss as heat. It involves collisions between the free electrons and the fixed particles of the metal, other free electrons and impurities. These collisions convert some of the energy that the free electrons are carrying into heat.


How is it measured?


livepaperhelp.com



The resistance of a length of wire is calculated by measuring the current present in the circuit (in series) and the voltage across the wire (in parallel). These measurements are then applied to this formula


V = I � R where V = Voltage, I = Current and R = Resistance


This can be rearranged to


R = V


I


Ohms Law


It is also relevant to know of Ohms Law, which states that the current through a metallic conductor (e.g. wire) at a constant temperature is proportional to the potential difference (voltage). Therefore V ¸ I is constant. This means that the resistance of a metallic conductor is constant providing that the temperature also remains constant. Furthermore, the resistance of a metal increases as its temperature increases. This is because at higher temperatures, the particles of the conductor are moving around more quickly, thus increasing the likelihood of collisions with the free electrons.


Variables


Input


Length of wire.


Material of wire.


Width of wire.


Starting temperature of wire.


Output


and thus the resistance of the wire. †








Voltage across wire.


Current in circuit.


Temperature of wire.


The variable marked with a will be varied, the other input variables will be kept constant. The output variable marked with a † will be measured.


Predictions


The longer the wire, the higher the resistance. This is because the longer the wire, the more times the free electrons will collide with other free electrons, the particles making up the metal, and any impurities in the metal. Therefore, more energy is going to be lost in these collisions (as heat).


Furthermore, doubling the length of the wire will result in double the resistance. This is because by doubling the length of the wire one is also doubling the collisions that will occur, thus doubling the amount of energy lost in these collisions.


Method


The following circuit was constructed to perform the investigation








wire








The two dots ( ) represent the crocodile clips that were placed at the ends of the required length of wire.


1. One metre length of 0.4mm diameter constantan (a metal alloy) wire is fixed to a metre rule.


. The first crocodile clip is clipped to the wire at the 0cm position on the metre rule.


. The second crocodile clip is clipped to the relevant position depending on the required length of wire.


4. The power supply is turned on. The voltage and current are then read off the ammeter and voltmeter, and recorded.


5. The power supply is then turned off and the second crocodile clip is moved to the next position.


The above steps are completed for each length and then the entire investigation is repeated for accuracy.


Rough Trials


In order to decide upon the voltage and lengths of wire to use in the final experiment, the following rough trials were carried out


At V


Length (cm)


Voltage (V)


Current (A)


Resistance (W) (to d.p.)





10


0.41


0.0


0.46





0


0.51


0.57


0.8





0


0.56


0.4


1.





40


0.60


0.


1.88





50


0.6


0.6


.4





60


0.64


0.


.78





70


0.65


0.0


.5





80


0.66


0.18


.67





0


0.67


0.16


4.1





100


0.68


0.15


4.5





At 5V


Length (cm)


Voltage (V)


Current (A)


Resistance (W) (to d.p.)





10


Could not be carried out as the wire simply melted.





0


.1


.07


1.0





0


.5


1.56


1.44





40


.4


1.4


1.88





50


.41


1.0


.6





60


.45


0.88


.78





70


.4


0.77


.





80


.5


0.68


.71





0


.54


0.6


4.10





100


.56


0.55


4.65





After performing these rough trials, it was decided that V would be used in the proper experiment, as it provided results from 10cm up to 100cm and the higher voltage provided no additional ease of measurement.


Furthermore, it was also decided to allow the wire to cool between experiments as considerable heat was noticed at lower lengths and, as mentioned above, an increase in temperature results in an increase in resistance. By allowing the wire to cool between experiments a fair test could be assured.


Safety


In order to perform a safe experiment, a low voltage of V was chosen so that overheating was minimilised. Furthermore, lengths lower than 10cm were not tried, which also helped to avoid overheating.





Please note that this sample paper on Resistance is for your review only. In order to eliminate any of the plagiarism issues, it is highly recommended that you do not use it for you own writing purposes. In case you experience difficulties with writing a well structured and accurately composed paper on Resistance, we are here to assist you. Your cheap custom college paper on Resistance will be written from scratch, so you do not have to worry about its originality.

Order your authentic assignment from livepaperhelp and you will be amazed at how easy it is to complete a quality custom paper within the shortest time possible!



No comments:

Post a Comment

Note: Only a member of this blog may post a comment.