Statement of the problem.
A technician has the problem of making wire resistors of various values. Plan and carry out an investigation to help the technician solve the problem.
Resistance is the property of a material, which opposes the current through the material. The larger the resistance the smaller the current flowing through the circuit. Resistance is measured in ohms (Ω). To find resistance we use the formula: resistance = voltage / current (R=V/I)
To find the current we must use an ammeter and to find voltage we must use a voltmeter.
In series circuits the total resistance is just the sum of all the resistance’s. In a parallel circuit the current through each component depends on its resistance. The lower the resistance the bigger the current that’ll flows through it.
There are four variables:
- cross section area of wire
I am going to test number one, the length of wire.
I predict that has I increase the length of wire, the resistance will also increase. The length of a wire affects its resistance to the flow of the charges through the wire. This determines how much current (i.e. flow of charge i.e. electrons) flows in the wire.
This is a preview of the whole essay
Types of variables
This is the length of wire we will use in the circuit in which the current will flow and the voltage.
This is what we measure; this will be the current and resistance.
This is what is kept the same. This will be the other variables: temperature,
cross section area of wire and material.
6 X lead
3m of wire
We must wear goggles has we are cutting wire.
We must also not work near water incase we get an electrical shock.
- I will collect all my apparatus, I will put on my goggles
- I will measure 300cm of wire
- I will set up the circuit as that in the diagram
- I will measure 30 cm of the 300cm of wire and will not cut it (this will save the wire being used up)
- I will place the crocodile clips between the 30cm of wire
- I will place the lab pack on full power and turn it on
- After doing this I will move the variable resistor until the voltmeter reads 1, I will then record the reading on the ammeter in my table.
- I will repeat step 8 but change the voltage to 2
- I will repeat step 8 but change the voltage to 3
- I will repeat step 8 but change the voltage to 4
- I will repeat step 8 but change the voltage to 5
- I will repeat step 8 but change the voltage to 6
- I will turn the lab pack off.
- I will repeat steps 5 to 14 this time measuring 90cm
- I will repeat steps 5 to 14 this time measuring 150cm
- I will repeat steps 5 to 14 this time measuring 210cm
- I will repeat steps 5 to 14 this time measuring 270cm
- I will but all the apparatus away
- I will work out the resistance, To find resistance we use the formula: resistance = voltage / current (R=V/I) and from this work out the average for each length
- I will draw my graph
How that I have carried out my experiment I must draw tables and from the tables draw graphs.
My graph confirms that as the length of wire increases so to does the resistance. My prediction was correct, it stated that as I increased the length the resistance would also increased.
I did not carry out my experiment out to plan. I only used 270cm of the wire and if I went on to use 6 volts the temperature of the wire would have increased; this would effect the results and ohms law. Otherwise my method was followed accordingly.
The resistance of a wire increases with length. That was my prediction. I used the same type of wire and measured the voltage across the wire and current flowing through the wire, 6 times. Then I changed the wire for a longer piece and repeated the experiment. I have done this with 5 different lengths of wire and I drew a graph for the values for each length of wire.
Resistance opposes the flow of electricity through my circuit. If I increased the length of wire I would have a greater resistance, this is because the electrons are being slowed down by other particles in the way. So if you increase the resistance you decrease the current.
I would carry out the experiment again this time using more wire to see what change that would do to the results and the averages. I might also do the experiment again, but this time increase the length of wire. To see what effect this has on the experiment.
The technician would use my graphs to find out how much wire he/she would need for each resistance.
Take for example if the technician wanted to know how much wire he/she would need for 20omh’s he/she would use the graph by going up 20omh’s in the graph and go across until he/she met the line and then go down. The length of wire in this case would be 90cms.