The resistance in a wire experiment Free essay! Download now
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The resistance in a wire experiment
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| Words: 1600 | Submitted: 02-Jan-2009
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Descriptionwe investigate how the resistance across the wire changes with change in several physical variales : eg the thickness
• The power supply which produces at least 2 Volts because that’s the highest value I will be using.
• Ammeter: it has to be able to give reading to three significant figures, which are in Milliamps.
• Voltmeters: this voltmeter has to be connected in parallel to the component in order to function properly. The reason I’m using it is to make sure that the Potential difference across my circuit is 2 volts all the time. (It has to give reading which are rounded to 3 significant figures)
• Also I will use a micrometer to find the cross area of the wire which I need to work out he resistivily of the material.
Good connecting wires which will connect my circuit and make a good connecting path for the current to flow through.
• Dependent variables: The resistance and the current
• Controlled variable: the temperature and material of the wire
Note: I will in fact keep the potential difference constant since:
Voltage= current × resistance
It is essential to keep the voltage constant to see how the current changes so I will be able to work out the resistance. By dividing the voltage by the current, the results I get are the resistance value.
I think as the length of the wire increases, the resistance increases as well this is due to the fact that the chances of the elections colliding with the Ions increase causing less electrons to flow. In other words, there are more collision causing less current to flow and thus the resistance is increased.
The ranges of my readings:
For the voltage the limits will be between 0 to 2 volts. The reason for this that did a quick preliminary experiment to have a rough I idea of what ranges I need. So I found out that the wire gets too hot between 2volts and 3.00 volts, so I decides to not pass 2V for safety and also that I think it will enough because it will give me the readings I need.
On the other hand, I also find limits for my current as well, which is between 0.00 amps to 0.90 amps.
• Before you start the experiment ask you teacher to check if it is connected in the correct way.
• Do not turn on the power until the whole circuit is connected.
• Do not change the wire change/touch the wire while the power is on.
• Do the experiment is place where there is no water, because the water is good conductor.
1. I will connect the wire with the circuit but with the ammeter in series and the voltmeter in parallel to the wire.
2. I will make sure that everything is connected the right way by asking my teacher to check.
3. I will connect the wire with a length of 10 cm. Then turn on the power supply. I will increase the voltage steadily until it reaches 2 volts.
4. I will write down the reading on the ammeter.
5. I will do the same method but this time I will increase the length by 10Cm until I reach 100Cm.
6. I will take two readings for current, and then I will use these values to find out the average.
My predicted graph:
For my second part of my experiment which is about finding the resistivity from my results I will use the equation below to find it:
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