If a conductor obeys Ohm's Law, the current will increase in proportion to the voltage. If you double the voltage, the current will also double.
Thick and thin wires
Thick wires work just the same as resistors in parallel - they let the electric current through more easily than thin wires.
The electrical of a wire would be expected to be greater for a longer wire, less for a wire of larger cross sectional area, and would be expected to depend upon the material out of which the wire is made. Experimentally, the dependence upon these properties is a straightforward one for a wide range of conditions, and the resistance of a wire can be expressed as
The temperature might affect the resistance of metals. Here are some measurements of resistance of some metals in different temperatures.
Prediction:
From the background information that I have gathered I predict as the length of the wire increases, the resistance of the wire increases. This is because increasing the length of the wire means that you are increasing the number of positively charged nuclei in the wire. This causes the increase of the collision of the negatively charged to increase, therefore the moving speed of them decreases (They slow down).
Apparatus:
100cm Ruler Ammeter
100cm Wire Voltmeter
Power Pack Crocodile Clips
Variable resistor Masking tape
Diagram:
The following circuit was constructed to perform the investigation.
Method:
- I set up all the equipment as shown in the diagram
- I connected a crocodile clip to the 0cm point and the other one to the 20cm point of the wire.
- Then I turned the power pack on and changed the variable resistor to a point that the voltmeter was on 1volt.
- I took the measurement of the current flowing through the circuit from the ammeter.
- I took the measurements in a table.
- Then I did the same but changing the length of the wire.
Fair Test:
In this test I will have to keep these measurements the same:
- The voltage will always be on 1.
- The same metal of the wire and the same thickness of the wire.
Results:
The first round of testing I thought that the results are wrong. This was because I did not change the variable resistor to get the voltage on 1V. I had to do the test a third time, and I got them right.
I have drawn a line of best fit on graph B. I have also drawn a best-fit line on graph A.
Conclusion: As predicted and from the graph I can see that as the length of the wire increases the resistance increases. This is because when the length of the wire is increased the amounts of negatively charged electrons are increased and so are the positively charged nuclei. With more nuclei the movement of the free electrons cause more collision in the wire. The collisions mean resistance. The collision also releases energy that is exposed as heat from the wire. If the wires cross-section is wider the resistant is lower, because there is more space for the free electrons to move. The graph is a line passing through the origin. The length is directly proportional to the resistance of the wire. This means that if you double the length of the wire the resistance doubles too.
Evaluation: I think my results are quite accurate, because most of the points are on or close to the line of best fit. Drawing the graph and the line of best fit was easy which shows the accuracy of the results. The first round of testing my results were completely out of order and I had to repeat the test twice. I had no anomalous results, because I repeated everything twice. The experiment could have been done better and more accurate if:
- The wire was straighter, so that the measurements were more to the point.
- The hot wire had been cooled down before doing another test on it. Heat makes the wire resistance more, because the movement and the collision of the electrons increase.
