Jamal Muse 10H
Science Investigation- Resistance Of Wire
Aim- To investigate how the resistance of a wire changes with length.
The dependant variable is the resistance of the wire.
The Key Variables are:
1. Wire length
2. Material
3. Wire diameter
4. Temperature
5. Wire Density
Wire length:
If the length of the wire is increased, then the resistance will increase. This is due to the electrons having a longer distance to travel and so more collisions will occur. Due to this, the length increase should be directly proportional to the increase in resistance.
Material:
The type of material will effect the number of free electrons, which are able to flow through the wire. The number of electrons depends on the amount of electrons in the outer shell of the atoms, so if there are more atoms then there are more electrons available. If the material has a high number of atoms, there will be a higher number of electrons. This will cause a lower resistance because of an increase in number of electrons.
Wire diameter:
If the wire diameter is increased the resistance will decrease. This is due to the increase in space for the electrons to travel through. Because of this increased space between the atoms, there should be fewer collisions. If the cross-sectional area of the wire were greater, the resistance would be less because more current will be able to flow through the wire.
Temperature:
If the wire is heated up, the atoms in the wire will start to vibrate more rapidly. This will cause more collisions between the electrons and the atoms, due to atoms moving into the path of the flowing electrons. This increase in collisions means that there will be an increase in resistance.
Wire density:
If the wire has a higher density, the resistance will be higher. This is due to the wire having more atoms in a smaller space, creating smaller and less gaps for the electrons to flow through. Because of the increased lack of space there should be more collisions.
To help me choose which factor I shall investigate, I am going to consider how I will measure each factor and which factor would be the best to record.
To measure the wire width, I would use a micrometer to measure the widths of the same length and material of wire e.g. Constantin 22, 23, 23 etc. I would use the same voltage and I would record the resistance for each length of wire. Although these results would be easy to obtain a record, the data graphs that would result from these would not be interesting.
For temperature of the wire, I would not be able to conduct a fair test, as it is extremely difficult to control and produce the correct range of temperatures needed without the correct equipment.
If I chose to measure the difference in the resistance in different materials, I would choose a number of different materials, but using the same voltage. I would record each resistance given by the same length and width. However, this will also produce graphs that will not be interesting and will not produce a connection between the materials and resistance, because of the materials I could test with the equipment available.
If I chose to investigate the effect of density on the resistance of wires, I would not be able to do this, as there is no way of measuring different densities of the wires
The final factor left to consider is the effect of wire length on the resistance of wires. To measure and record these findings for this factor would be simple, and the results should show a connection between the length of wire and the resistance produced by the wire. This is why I am going to investigate this factor: the wire length.
