Aim:- my aim is to investigate how the addition of equal length wires [in parallel] effects the resistance through the bundle of wires.
Constant Variable/s:- I will keep all the following the same so it can’t effect my experiment, and will be a fair test. Length of the wire, thickness of wire, use the same material of wire [nichrome], do the experiment at room temperature, Use the same multi-meter so that the voltage stays constant and I will use the same kind of wire from the same batch. And where possible the same connecting wires.
Changing Variable/s:- this will be the number of strands of wire in the bundle.
Prediction/s:- I predict that the resistance in the bundle will be inversely proportional to the number of wires In the bundle. R=1/N where R stands for resistance and N stands for numbers of strands in the bundle. So as the number of wires in the bundle increases the resistance through the bundle will decrees. E.g. doubling the number of wires will half the resistance. I thing this because the wires will be connected in parallel, and this for means the electrons have more than one option in the way they want to travel. This is the same as saying a road with one lane is going to travel slower and be more congested than a road say with three lanes, which will have more space to travel it therefore can travel quicker in.
Apparatus:-
A multi meter Selotape
3 connecting wires [red and black] Role of wire to test
2 crocodile clips A 100cm [1m] Ruler
Scissors Wire Cutters
Method:-
- Set up apparatus as shown in “apparatus Diagram”
- Length of a strand of wire should be 100cm [1M] long each. Diameter of 0.315mm
- Attach the strand to the 1M ruler as shown in the diagram “connect and holding wire/s”
- Adjust the multi meter to the ohms section and put is on the 200.
- Put the connecting wires in the V socket and the common socket.
- Clip the crocodile clips to the end of the wire/s.
- Record the resistance shown on the multi meter, accurate to one decimal place, in a table.
- Repeat steps 1-7 for 1-6 strands in the bunch. Making sure the wires only touch at the ends.
- Then repeat the whole of steps 1-8, about four times, so any mistakes can be spotted and discounted.
Safety:-
- I will be careful while handling the wires as they have sharp end and can easily puncture your skin.
- I will be careful no to get the circuit wet, as this may lead to me getting an electric shock.
- I will be careful when cutting the wires and selotape, with the Sharpe scissors
Results:
Length:- 100CM [1m] Temperature:- Room23°C
Thickness:- 30 SWG or 0.315 mm Voltage:-
I had planned to only use thirty cm lengths of wire, but this proved impractical because the resistance was to small using 30 cm so I decided to lengthen the wire to 100cm [1M] lengths. This would therefore give me a better indication into how the resistance changes.
Conclusions:-
As you can see from my results table of results and my graphs my experiment proved that there was a connection between the number of wires in the bundle and the resistance it the bundle. My prediction that the resistance in the bundle will be inversely proportional to the number of wires In the bundle, was not in fact true but I was all most correct as four strands the resistance was 3.6 ohms and with only two wires the resistance was 6.9 ohms so it was almost double so I think in perfect conditions I think my prediction would have been correct. My only point that on my graph that looks out of place was in set 1 for 4 strands this proved to be an anomalies. [see why in evaluation]. It think it was a wise decision to change the length of the wire from 30 cm to 100cm as this made the numbers easier to handle and seemed to show the Patten more clearly. The safety precautions proved to be sufficient as I was not hurt or injured in anyway. My results were better shown on the graph connected by a smooth curved line as the resistance didn’t decrees at a uniform rate, therefore the curve shows this better. All though as on my graph I predicted a different line. As all my results bar one follow the same trend I can conclude that as the number of strands in the bundle increases the resistance decreases but it doesn’t do this at a uniform rate though I think in perfect conditions it would be uniform. As shown on my graph of resistance reciprocal against number of strands. The line on this shows that the resistance is inversely proportional to the number of strands. Therefore my points aren’t too far off this line so I think in perfect conditions all points would lie on the line. I believe this because of the way resistance works, describes above, We see that if the area of the wire doubles, so does the number of possible routes for the current to flow down, therefore the energy is twice as spread out, so resistance might halve. And my results were almost showed this. 1 strand has an average resistance of 13.6 ohms where as 2 strands had an average resistance of 6.9 ohms which is almost half.
Evaluation:-
I can say that this experiment was almost successful apart from it didn’t quite give the result I expected. My method could have been improved if when I was repeating the experiment I had started with 6 wires and then took a wire off each time as it was difficult to take all the wires off the ruler as they were attached with cello tape. To get more accurate results I could maybe repeat the experiment more times and use a standard test circuit instead off a multi-metre. Things that might effect the resistance are the different length connection wires, resistance of them and the resistance of the crocodile clips. As well as the crocodile could be oxidised. If I was to repeat the experiment I would also take a measurement of no wires. My experiment also contained one anomalies result this could be due to me missed read the multi-meter reading.
For further work I could see if length or diameter or material or temperature of the wire effects the resistance.
