To find what affects the resistance of a piece of wire. Prediction I predict that as long as I increase the length of the wire, the resistance of it will increase. Wire is made up of particles that are all made up of atoms. The more wire there is, the more atoms there will be. This affects the resistance of the wire. Resistance is simply defined as the ease with which electrical current passes through a substance. If I were to predict what the graph would look like, it would be like this: The reason for this is that I believe if I double the length of the wire, the resistance of the wire will double.
Inside a substance the atoms are constantly vibrating and, the more vibrating atoms there are, the greater the difficulty there is for the current to pass through it. Some of my prediction was based on my preliminary tests/trials. Length of wire (cm) Current (A) Voltage I also think that there will be some kind of correlation between the resistance of the wire and its length.
The reason there is no result for 20cm is that the wire got damaged, and prevented me from reading the meters properly. This has led me to the conclusion that in the actual experiment we would only go down to 20cm. We also decided to go down in 5cm; this would give us more, and more accurate results. Method I will measure the resistance by using the formula R=V/I. This is Ohms Law and will hopefully ensure relatively accurate results. I will have a normal circuit, but the Ammeter will be in series and the Voltmeter will be in parallel.
The circuit will look as follows: (PTO) Safety I must make the area safe in order to conduct the experiment safely: 1. I must be sure to conduct the experiment well away from sinks, or any source of water. 2. I must be sure to have dry hands whilst conducting the experiment. 3. I must not use over 6V or under 10cm of wire to ensure there are no over heating problems. Apparatus In order to conduct my experiment properly I will need the following apparatus: A length of wire 1m long A meter rule 2 multi-meters Some leads.
Some crocodile clips A power pack Fair test In order to make this experiment fair, I will have to: 1. Make sure that the piece of wire that I use is the same piece the whole way through the experiment. Also ensure that that piece of wire is made of the same metal. The reason that this is important is that, copper for example has a very low resistance compared to other metals such as nichrome. 2. When a metal resists, heat is produced. Due to this the wire may expand, thus making it more difficult, or easy for the current to pass through it.
It is because of this that I have decided that I will leave the wire for 2 minutes after each test to let it get back to its original temperature before starting again. 3. The area of the cross-section will also affect the resistance of the wire because the wider the area, the more wire there is for the current to pass through. This is another reason why I shall need to use the same wire all the way through. 4. I must also ensure that the reading on the power pack is constant, as a change in the voltage would ruin the experiment.
I must also make sure that the power pack is set on DC mode, or direct current. The reason for this is that alternating current would confuse the readings on the multi-meters. Variables We have been instructed only to vary the length of the wire, rather than anything else. From my rough trials I have decided to keep the voltage low in order to ensure that the wire does not get damaged, thus hindering the rest of the experiment. Results Length (cm) 1st Experiment Current 1st Experiment Voltage 2nd Experiment Current 2nd Experiment Voltage 3rd Experiment Current 3rd Experiment Voltage.