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How can you change the level of current flowing in a metal wire?

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How can you change the level of current flowing in a metal wire?

There are many factors which affect the current in a wire. The four main factors which affect this are.

  1. Voltage
  1. Thickness
  1. Length
  1. Type

All of these types of resisters can be calculated by using ohms law. Which states ‘If it takes 1 volt (1 joule per coulomb) to push a current of 1amp through a resistor, it has a resistance of 1 ohm’.  The equation for this is:

R=V

                                                 I

The R stands for Resistance, the V stands for voltage and the I for amps.

The atoms in any wire are obstacles for the current (flow of electrons) to over come.

The Voltage affects the level of current through a wire due to it being the driving force. The voltage pushes the current through the wire. The higher the voltage the more current will flow. The higher the voltage means the higher the driving force behind the electrons which makes it easier for them to get through the atoms in the wire, the higher the level of current flowing in the wire.

The thickness of the wire changes the resistance. The Thicker the wire the less resistance than a thinner wire of the same material.  This is because the electrons jump from atom to atom. A wire with a large cross section can allows more electrons to flow in a bigger surface area. The thicker the wire the lower the resistance. The thickness of wires is inversely proportional to its cross section. So when the thickness of the wire doubles the resistance will be halved.

The length of the wire also affects the flow of current in a wire. The longer the wire the more atoms the electrons have to get through. The longer the wire the further the electrons have to travel through material, more collisions with the atom thus the higher the value of resistance.  

The type of wire also affects the flow of current in a wire. This is due to the difference in the number of free electrons in the wire. The more free electrons the less energy needed to be spent. Different materials have specific uses.

If I tested the type of wire it would be extremely hard to confirm the resisting capacities. So it would be hard to make an accurate hypothesis. If I tested the different diameters of the wires there isn’t a wide range of diameters I could use. I have decided to use the length of the wire as the variable and keep all the other variables the same. I have chosen the length because I can be very accurate with the length of the wire and use a wide range of lengths to test the resistance of the wire.

Method

  • I am going to measure the length of the wire using the same ruler so I always get an accurate length.
  •  Then I’m going to apply the current. I’m going to use the same equipment to make the experiment fair.
  • Then I am going to wait until the ammeter shows a stable result then record this measurement.
  • I’m going to repeat this for each measurement three times then work out the average. I’m going to so this to get an accurate reading and to check that one of the measurements wasn’t an anomaly. Also to check that my results are reliable.
  • Also every time I do the experiment I’m going to use the same type of wire.
  • Also as the current goes through a wire its gets very hot and to be safe I’m going to leave the wire for a few minutes before changing the wire.
  • Also I am going to use the same type of wire which will be constantan. Which will has a diameter of 0.4mm
  • I’m going to use a piece of wire with a gauge of 34.  
  • I’m going to keep the voltage constant at a voltage of 2 by changing the variable resister and check the voltage on the voltmeter and keep it at two within a small margin of error.

This will be repeated for each length of wire three times to ensure that the results are accurate.

My hypothesis is as I double the length of wire which will double the resistance the flow of current through the wire will half.  This is due to the longer the wire the more atoms the electrons the atoms have to get through and the more the resistance the less the current.

I decided to do a set of preliminary results I will use these results to ascertain whether or not the range of the lengths of wires I have chosen are viable to use in my experiment.  

Results

Preliminary

Length of wire mm

Current no 1 in amps

Current no 2 in amps

Current no 3 in amps

Average current in amps

200

0.57

0.57

0.56

0.57

100

0.15

0.15

0.14

0.15

The preliminary shows that the range of the measurements I have chosen are very feasible to test.

These are the other results I collected. I used a 34 gauge wire constantan wire which was charged at a voltage of 2 volts.  

Length of wire mm

Current no 1 in amps

Current no 2 in amps

Current no 3 in amps

Average current in amps

Resistance in ohms (R=V/I)

200

0.57

0.57

0.56

0.57

4.0

300

0.36

0.39

0.39

0.38

5.0

400

0.29

0.29

0.29

0.29

7.0

500

0.24

0.23

0.24

0.24

8.0

600

0.2

0.2

0.2

0.2

10.0

700

0.18

0.17

0.18

0.18

11.0

800

0.16

0.16

0.15

0.16

12.5

900

0.14

0.14

0.14

0.14

14.0

1000

0.15

0.15

0.14

0.15

13.0

Analysis

The graph shows that as the length of wire increases so does the resistance. The graph shows a best fit line which is near enough directly proportional. It shows as the length of the wire increases the amount of atoms the electrons have to over come is increase thus making it harder for the electrons to move through the wire which increases the resistance.

I am now going to test my hypothesis I will do this by choosing a length and checking the resistance then doubling that length then checking that length. In my prediction I stated that the resistance will double as the length doubles.

The first measurement I have chosen to test my hypothesis on is 300mm which shows a resistance of 5 ohms. The measurement of 600mm has a resistance of 10ohms. This shows my hypothesis is correct so far. It also shows that as the length of the wire doubles so does the amount of atoms which doubles the amount of collisions between the atoms and the electrons thus doubling the resistance.

The second measurement I have chosen to test my hypothesis on is 400mm this shows a resistance of 7ohms. The measurement of 800mm has a resistance of 12.5ohms.  Although the resistance is not exactly double it does show a slight connection I have to allow for a margin of error.  I expected the amount of resistance for a length or 800mm to be 14ohms. Although there is only 1.5ohms away from my prediction in my hypothesis.

The third measurement I’m going to test my hypothesis on is 500mm this shows a resistance of 8ohms. The measurement of 100mm shows a resistance of 13ohms. These results also do not exactly follow my hypothesis but they are very close. By following my hypothesis I have worked out that the resistance for 100mm should have been 16ohms.  Although this result could have been taken wrong it could be an anomaly. Due to many factors which could have been wrong in the experiment.

Evaluation

The results clearly show that my hypothesis was very accurate. The Results I collected were also very accurate. Although there is a slight irregularity for one of the results. The result which does not correlate with my other results is the wire with the length of 100mm. This anomaly could have been caused because of many factors. Such as the measurement of the wire may not have been accurate which would have affected the distance the electrons had to travel if the measurement would have been too high there would have been a longer distance which would have caused the electrons to collide into more atoms and increase the resistance. This may have occurred due to kinks in the wire. I could have measured the voltage wrong at the beginning of the experiment. If the voltage was lower than 2 volts this would have caused a higher driving force to push the electrons through the wire and caused a lower resistance. Also there could have been a kink in the wire which would have caused a further obstruction for the current of electrons to go through. The other error which could have occurred to have caused this anomaly is the temperature could have been higher or lower than when I did the other experiments. This would have caused the electrons to loose kinetic energy and move slower through the wire and increasing the resistance. Also the temperature of the wire could have effected the movement of the free electrons giving them thermal energy and cause them to move faster. This would have increased the rate in which the current flowed.    

I could have improved this experiment in many ways. Such as I could have taken more measurement which would have resulted in more accurate averages which would have made the calculation to work out the resistance more accurate. I also could have used a wider range of results and taken higher and lower measurements.  I could have changed the voltage and kept the length the same and see how that effected the current in the wire. I could have investigated how the diameter of the wire affects the current and kept the voltage and the length of wire the same.      

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