Physical - Circuit

GCSE Science

Science Investigation Report Daniel

F5D

P O A E

6 6 6 4 24/30

Name: Daniel Shih

Class: F5D

Teacher: Dr. Aravind

School: Kiangsu-Chekiang College International Section

Date: 30th November, 2006

Index

Introduction

Planning – Aims, Variables, Fair Test, Prediction, Hypothesis

Planning – Apparatus, Procedure

Planning –Procedure of temperature, measurement, safe rules

Obtaining

Analyse – Table 1

Analyse – Table 2

Analyse – Table 3

Analyse – Table 4

Analyse – Table 5

Analyse – Table 6

Analyse – Table 7

Analyse – Table 8

Analyse – Compare and Contrast

Evaluation, Conclusion, Bibliography

Introduction:

What is an electrical circuit?

An electrical network is an interconnection of such as the , and . We use circuit to measure the voltage, and also the current of some conductors which can transfer the electricity. To design an electrical circuit, first we need to be able to predict the current and the voltage.

What is electrical resistance?

Electrical resistance is a measure of the voltage divided by the current flows in the electrical circuit. The unit of resistance Is Ohms,Ω. The quantity of resistance in an electric circuit determines the amount of current flowing in the circuit for any given voltage applied to the circuit. The way of measuring the resistance in a circuit is:

“R” is the resistance of the object, measured in .

“V” is the potential difference or the voltage across the object, measured in .

“I” is the current passing through the object, measured in amps

So what are the uses of electrical circuit?

This is a test to find out the best conductor in metals, the higher the resistance, that means the better the metal could be used to pass the electrons through.

Also, the temperature of the metal will affect the amount of electrons flows at each time, by heating the metal up, it would expand and allows more resistance; so the temperature were low, it might can’t conduct electricity at all.

Planning:

Aims:

In this experiment, I will try to prove the thicker the wire; the more the resistance, there would be and also the more current flowing flows per second. And also to prove that “Copper” wire will have the highest current flow by time each second.

Variables:

The low-voltage wires used in the experiment.
The low-voltage power supply used.
The materials of the wires used.

Control Variables:

The diameter of the wire used in the experiment.
The length of the wire should be measure before the experiment.
The temperature of the wire from room temperature to 80°C.
The amount of charge flows in the circuit.

Fair Test:

In this experiment, I would first make sure that the ammeter and the voltmeter were perfectly set, if we did not set it well, this will affect our results of resistance.

Also I have to make sure all the crocodile clips I used have the same materials, or else the flow of charge would be different. The diameter of the wires should be equal, this is going to keep the flowing charge remained to be the same.

The switch must be working well, or else we can’t switch it on, that means we can’t start the experiment well.

The light bulb better is working as well, or else there might be some problems getting the results of the resistance out.

Repeat the experiment for two more times to check the results.

Prediction:

By setting everything well, I predicted that by using a diameter of 1.25mm wires will have the highest amount of resistance compare to the diameter of 0.45mm wires, this is because that it can allow the greatest flow of charge to pass through.

The materials of the wires could be affecting the experiment, as we used the wires of copper, the results should be better than using constantan because they allows more current to pass through in time, therefore can transfer more energy.

Hypothesis:

It is likely to be seen that because the greater of diameter, the more the charge could be flow by time, there were larger space to allow charge to pass through.

According to Encyclopedia website, I have discovered that a copper wire is easier to be used for experiment, because of its reactivity series, it will have a least resistance compare to the Nichrome and Constantan wire.

Method:

Apparatus:

Safety goggles
Ammeter
Voltmeter
Switch
Variable resistor
Bulb
Wires of copper with crocodile clip
Power Supply
Constantan wire with 0.45mm diameter, 0.9mm diameter, 1.25mm diameter
Copper wire with 0.9mm diameter
Nichrome wire with 0.9mm diameter

Procedure:

Prepared all the apparatus that needed.

“Change Symbol I to A”

Connect the switch with the power supply with a wires
Connect the other side of switch with the variable resistor by using another wire.
Set the ammeter on the other side of the constantan wire.
Set Voltmeter parallel to the constantan wire.

This is a preview of the whole essay

Method:

Apparatus:

Safety goggles
Ammeter
Voltmeter
Switch
Variable resistor
Bulb
Wires of copper with crocodile clip
Power Supply
Constantan wire with 0.45mm diameter, 0.9mm diameter, 1.25mm diameter
Copper wire with 0.9mm diameter
Nichrome wire with 0.9mm diameter

Procedure:

Prepared all the apparatus that needed.

“Change Symbol I to A”

Connect the switch with the power supply with a wires
Connect the other side of switch with the variable resistor by using another wire.
Set the ammeter on the other side of the constantan wire.
Set Voltmeter parallel to the constantan wire.
Check the circuit is built well.
Switch the power supply to a voltage of 4V.
Move the resistor to protect the ammeter, and keep it fixed.
Turn the switch on and record down the voltage and the amp down.
Calculate the resistances by using potential difference (in V) divide by current (in A).
Plot a graph to show the results.
Repeat the experiment for 2 more times to check the results.
Re use this method with the rest of the constantan wires and copper, nichrome wires.

Procedure of temperature:

By raising the temperature, copper wire should be used.
Follow the method above until step 8.
Put the water with room temperature into a beaker.
Put the wire into the water.
Switch the power supply on and record down the voltage and current for three times.
Add boiling water at 80°C and put the wire in. Record the voltage and current down for another three times.
Wait until 50°C and record anther result down.
Plot a graph to see the differences between this experiments and the rest.
Calculate the resistance using voltage divide by current.

Measurement:

In the experiment we have to make sure the batteries were new, so hopefully it would have the same amount electrons. So the flow of charge won’t be a different from the results. By checking we use the Power Supply, it can be very accurate of given out charges into a circuit.

Also, the length of the wires must be the same for all three of the metal wires, and the diameter should be 90mm. By testing this we could plot a point every 5 centimetres to make the length equal, and measure the diameter with a screw guage

Safety rules:

Wearing safety goggles can protect our eyes from getting damage.
Beware of the flowing charge; do not play with it while the experiment was weren’t finish.
Make sure the wires don’t have crack, or else might give a shock to the person who touch it.
The ammeter and voltmeter are heavy enough; do not throw it around as toys.

Obtaining

In this experiment, we have occurred lots of interesting parts. The first times we start the experiment our circuit were set awfully, this affect the results we get at the start.

With out putting a variable resistor in, the ammeter was out of the range, and seems to be not working well. And the constantan wire with 5 centimetres was heating up, and it changes its colour from silver into golden red and very shiny. This is the first time and the last time this mistake happened in our experiments.

By resetting up the circuit, we learned about how to use a variable resistor. A resistor can be use as protecting the ammeter; therefore we set the resistor at a fix spot and switch on the switch again. This time, our result seems to be as what we expect to be. This experiment we’re using the constantan wire with the thinnest diameter, 0.45mm; we first set it with 5cm, and achieved a result without mistakes. After we try it for another three times, we then change the length to 10cm, the voltage increase and the current dropped. As the length goes up to 30cm, the voltage is twice as much as the 5cm results, and the current is only half of the 5cm results we got.

After using the constantan wire with 0.45mm diameter, we change the wire to constantan wire with 1.25mm as diameter; this is the thickest diameter we got in the experiment. Before we start the experiment, I predicted that this would have the highest resistance out of all three wires with different diameter. When we uses 5cm of wire to test the experiment, the current is about to be 3.6amps, and the voltage is about to be 0.1, by increasing the length to 30cm the voltage becomes 4 times than before, and the current only drops 0.3amps. When we touch the wires it were very hot, I believe this is because the wires were having a high resistance.

The third experiment we used the constantan wires with 90mm as diameter. By measuring it from 5cm until 30cm, we’ve found out that it have the highest resistance, even more than the thickest wire, either there was a scientific error, or it just work like this. The first try we have a voltage of 0.2V, but a current with 3.5amps, this showed me an error must have occurred. By increasing the length the voltage increase and the current dropped again.

The fourth experiment were still using the same wire, but with a longer length. We first start with 35cm, and get a higher resistance as what we expect, which were good. By adding up the length up to 60cm, it have a voltage with 0.6V and 1.45amps, this makes the resistance about to be twice as much as the results with 30cm.

Then we changed to Nichrome wire, with 90mm as diameter, and set it into the circuit. We first get 0.4V and 3.6amps while having it with 5cm as length, then when we increase the length to 15cm the voltage rise up to 0.85V but the current drops down to 2.9amps. However, comparing to the constantan wires it has a higher amount of resistance.

Then we use copper wires with diameter of 0.9mm for experiment. We test it for 5cm it have a very low rate of Volts and current compare to the one we done before. The flow of charge was lesser in copper wires compared to the rest.

When we test the copper wire of 100cm long with 0.9mm diameter into water, it have a results of room temperature with low resistance, when the water were starting to boil, the current and the voltage both raise, and the resistance also raise with 0.5ohms. As the water cools down the resistance drop again, this can show that temperature will affect the flow of charge as well.

Analyse

Table 1: This table shows about the thinnest wires used in the experiment, Constantan wire with diameter of 0.45mm.

In this table, we could be able to see that the resistance of the wire were increasing by length. This means constantan wire with diameter of 0.45mm can be use as a conductor; however, it can’t transfer too much charge at one time.

Table 2: This table have the results about the thickest wires used in the experiment, Constantan wire with diameter of 1.25mm.

In this graph, we could see that the resistance of the wire were increasing as the length increases. This means constantan wire with diameter of 1.25mm can be use as a good conductor. It nearly occurred in a straight line if the resistance of length 5cm were higher a little bit.

Table 3: This table tells about the normal wires used in the experiment, Constantan wire with diameter of 0.90mm.

In this table, I can see that the resistance weren’t stable. With the length of 20cm, this might because of the ammeter have some problem while we’re measuring. I believe if we have a chance to retry it over again, we should get better results as what we have expected.

Table 4: This table shows about the normal wires used in the experiment, Constantan wire with diameter of 0.90mm, however is longer than the one before. Error*

As the table shows above, the resistance of the length 5cm and 10cm were equal, and then it suddenly decreases. This shows there’s an error; I think it happened because we didn’t set our circuit in the correct positon.

Table 5: This table shows the details about normal wires used in the experiment, Constantan wire with diameter of 0.90mm, however is longer than the one before, retry.

This seems to be nice results as it shows; the resistance were rising up slowly as the length grows. It proved this is a nice experiment, and let us understand this wire could be use for transferring the current through.

Table 6: This table gives the results about the different kind of wires used in the experiment, Nichrome wire with diameter of 0.90mm.

This graph shows a very clear results, the increase of resistance were easy to see, from the positive correlation shown. This means that this is quiet a good test, it don’t seems to have any error in this experiment.

Table 7: This table gives the details about the third wires used in the experiment, Copper wire with diameter of 0.90mm.

This result shows the metal which can transfer the least resistance through by the differences of the length. It was mostly under 0.01Ω, this means that we can’t use this much as the time we’re transferring a large amount of currents.

Table 8: This table have the results which copper wires were heated in the beaker of water. Wire length equals to 100cm long. Room temperature were 24C°.

The last experiment we done, by putting a wire with length 100cm, diameter of 90mm into boiling water. Our result shows more clear on the table than the graph. As we can see, the resistance only raise a bit as the temperature goes up. But the difference from 30 C° to 50 C° were higher than what I expect, I think this is because of the temperature were not fix while we were recording our results down to our table.

Compare and Contrast

This is the averages of the 3 wires. By showing this on a graph we could be able to tell which wire has the highest resistance.

By reading the graph, we could see that Nicrhome Wire have the highest resistance out of the three wires, so we could tell that it can allows least current flow through each time compare to the rest of them. If one day we have to choose a wire from this three to pass current through, the best is using the Copper Wire, it got the lowest resistance which means it have a high amount of current can pass through per second. If we don’t want the electricity to flow through easily, we will choose the Nichrome Wire, because it only allows small amount of current to pass through each time. Constantan Wire was a normal wire, it can’t be use for high resistance flowing, but it can allow more current flow at each time compare to the Nichrome Wire.

However, we could see that the resistance were rising up no matter which materials of wire we have chosen, so that means they still conduct electricity, so we shouldn’t touch it while having this kind of experiment.

Compare and Contrast 2

This is the averages of the 3 different diameters of wires. By showing this on a graph we could be able to tell that which diameters can allows the most resistance to pass through.

By looking at the graph, we could see that Constantan Wire with 0.45mm of diameter have the highest resistance out of all. So we could tell that it can allow high amount of resistance but low amount of current flow through each time compare to the rest of them. The wire with diameter of 1.25mm can allows the lowest resistance, that means it could have highest current to flow through each time.

However, we could see that the resistance were rising up no matter which diameter of wire we have chosen, so that means they still conduct electricity, so we can use it to let current pass through.

Evaluation

In my experiment, I’ve found out there’s some error occurs. In my first results, by using the length of 15cm, the resistance seems to be a “little” bit different from the rest, so it didn’t showed as a straight line. This might because my circuit weren’t set correctly, so this error occurred.

For the second experiment I did, there’s seems to be a error at the second try of length 10cm, the number seems to be too “high” compare to the rest of them, I believe this happened because we accidentally crash the variable resistor.

Then in Table 3 we got an error again, the current of the wire seems to be a lot more higher, I’m sure this occurs because the resistor is not working well, and also the circuit were kind of messy, might affect the results we got.

Then we got an error results shows at Table 4, none of the results can fit with Table 3, there were the same wire, same diameter, only the length we tested is different, but the results we got were too out of range, so I can say that this is a failed try out. So we re-do the experiment using this wire again. I think that this happened because the ammeter is down, the current were keep increasing by every few seconds.

In Table 8, for testing the temperature, it seems to be a nice results, however the different of 50C° and 30C° were larger than what I have expect, so I could tell that the temperature of the water might not be as accurate as the time we measured. Also it might because some water spread out of the beaker, onto the wires; this should be changing my normal results.

Also, I’m not really sure about how the resistor works with ammeter; therefore by accidentally move it might decrease the accuracy of my results as well. The results of resistance might be different because the circuit we set weren’t exactly the same, therefore it might also be some differences compare to the first time, the first results we got. So, maybe next time we should have used the same circuit, and do all of the experiment in same time, and it might have a better results in future.

Conclusion

In my own opinion, I believe this is quiet a nice experiment, and I also get some good results as well. I’ve found out that my prediction was correct, about the copper wire with a diameter of 90mm will transfer the least energy compare to the rest of the two.

I also learned about the circuit of electricity, I could now tell how the current flowing was, and how it could be measured. By looking at the results I’ve got, I was really please, even though some mistakes happened in the experiment, but we still success to finish our experiment in the time limit, which is such a great thing to celebrate.

Resistor can be use to protect the ammeter, this is a very useful apparatus; I know the ammeter was an important character in the circuit while measuring the resistance. So if the ammeter were damage cause of the flowing current were too high, this will be a very bad news for us. So take care of the equipment is another important thing I learn from this experiment.

If I have a chance to repeat the experiment, I would be likely to set my circuit up just like this time, because there shall be less problems. And I might use the copper wire more often in the circuit, using copper wires it allows more current to pass through compare to the Nicrhome and Constantan wires, which might help in my future life.

Bibliography: