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.

Types of variables

Independent

This is the length of wire we will use in the circuit in which the current will flow and the voltage.

Dependant

This is what we measure; this will be the current and resistance.

Control

This is what is kept the same. This will be the other variables: temperature,

cross section area of wire and material.

Method

Apparatus

Lab pack

6 X lead

Variable resistor

3m of wire

Scissors

Ammeter

Voltmeter

Goggles

Safety

We must wear goggles has we are cutting wire.

We must also not work near water incase we get an electrical shock.

Diagram

Method

1. Start
2. I will collect all my apparatus, I will put on my goggles
3. I will measure 300cm of wire
4. I will set up the circuit as that in the diagram
5. I will measure 30 cm of the 300cm of wire and will not cut it (this will save the wire being used up)
6. I will place the crocodile clips between the 30cm of wire
7. I will place the lab pack on full power and turn it on  
8. 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.
9. I will repeat step 8 but change the voltage to 2
10.  I will repeat step 8 but change the voltage to 3
11.  I will repeat step 8 but change the voltage to 4
12. I will repeat step 8 but change the voltage to 5
13. I will repeat step 8 but change the voltage to 6
14.  I will turn the lab pack off.
15.  I will repeat steps 5 to 14 this time measuring 90cm
16.  I will repeat steps 5 to 14 this time measuring 150cm
17. I will repeat steps 5 to 14 this time measuring 210cm
18. I will repeat steps 5 to 14 this time measuring 270cm
19.  I will but all the apparatus away
20. 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
21. I will draw my graph
22. Finish

Blank table

How that I have carried out my experiment I must draw tables and from the tables draw graphs.

 

Tables

30cm table

 

90cm table

 

150cm table

 

210cm table

 

270cm table

 

 

Write up

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.  

Conclusion

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.  

Improvements

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.