Resistance relationship for a conductor Essay

Custom Student Mr. Teacher ENG 1001-04 12 October 2017

Resistance relationship for a conductor

Through it will experience low resistance to the rate of flow. 3. Different types of materials will affect the resistance in different ways. Materials such as copper, are very good conductors, and is used for connecting wires. Other materials such as nichrome (as used in the investigation) have a higher resistance than copper, and so is used in the heating elements of electric fires. 4. As the temperatures of a wire increases, the resistance of the wire increases as well. This is used in resistance thermometers, which use the fact that electricity does not flow so easily through a wire when the wire gets hot.

Resistance is the opposition to the flow of charge. In metals, a ‘sea’ of free electrons enabling it to conduct electricity surrounds a lattice of positive ions. The shorter the length of wire, the less energy is needed to move the electrons across the wire If the metal is attached to a power supply then the electrons flow through the metal but collide with atoms. Resistance is shown below in the diagram below: The resistance of a metal can be regarded as arising from the interaction, which occurs between the crystal lattice of the metal and the ‘free’ electrons as they drift through it under an applied potential difference.

This interaction is due mainly to collisions between defects in the crystal lattice (e. g. impurity atoms and dislocations) also play a part, especially at very low temperatures. Resistance is measured in Ohms (? ) Georg Ohm discovered that the current flowing through a metal wire is proportional to the potential difference across it (providing the temperature remains constant). Therefore: Resistance, R (? ) = Potential difference across the wire (V) ITable 1 shows the data recorded and the resulting values for resistance for each length.

These were those separate samples of the conductor tested for each length, and the average voltage was used to determine the resistance volume. Graph 1 plots the resistance against length for the range of test samples from 10cm to 100cm. The graph shows the data to be in very close proximity to a straight line, verifying the prediction to its length. From the best fit line drawn on the graph, the resistance per unit length of 24 SWG nichrome wire is found to be 0. 362 ohm/cm. When current passes down a wire, the wire gets heated.

The moving electrons collide with ion and cause them to vibrate thus increasing the temperature ths is a waste of energy-when a current flows, heat is transferred to the air surroundingggs which explains why computers get hot in operation. However we can make use of the heating effect e. g. in fuses which are designed to melt when too much current flows e. g. in kettles. We can calculate the heat transferred per second using the following formula:

From the table above we see that there is a relationship between the resistance and the current. We see that from the results table that the power (in Watts) is equivalent to the current (in amps) squared multiplied by the resistance of the wire. From the graph showing Power Vs Length, we can work out the heat transferred in one centimetre of nichrome wire. Power i?? Length =Thermal energy transferred (J) Length (cm)

Current (Amps) Power (Watts) From these results we can work out the coulombs of charge in each separate length of nichrome. This result will then allow us to calculate how many electrons had passed through the wire, which further allows us to calculate the time taken for the experiment to take place.

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  • University/College: University of Chicago

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  • Date: 12 October 2017

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