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What Variables Effect Omosis In Potatoes Essay Sample

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  • Pages: 9
  • Word count: 2,393
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  • Category: physics

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Introduction of TOPIC

Information about osmosis.

Osmosis is the movement of water molecules from a region where there is high concentration to where there is low concentration, this often occurs across a selectively permeable membrane. This is an area of selectively permeable cells that only allow certain substances to cross and prohibit others. The reduction in size of the chip may be due to this process.

In a plant cell – if it is put into pure H2O, it will not rupture because the cell wall is fully permeable to water so therefore osmosis can not occur.

Osmosis in a cell membrane – cell membranes are selectively permeable and if put into pure water it would swell because the cell wall is strong. They also do not burst but becomes turgid.

If a plant cell is put into a salt solution, water moves out of the cell and so the cell shrinks and becomes flaccid. This process is called Plasmolysis, the plant cell shrinks because the cell membrane tears away form the cell wall.

Aim

To find out what difference the concentration of a salt solution makes to the size of a raw potato chip.

I predict that that there is a proportional relationship between the current flowing through the wire and the strength of an electromagnet. Therefore this means that as one is increased then the other will increase. I think this due to the domain theory.

Normally without an iron core, when current is passed through a wire a magnetic field is created along the axis of the wire coil. Although despite this the field is not very substantial, yet when an iron core is inserted into the wire coil, the magnetic field that is flowing in the direction of the axis, alters and arranges the domains within the iron to an attractive polarisation. It is due to this fact that the change of domains in polarisation greatly increases the strength of the magnet; therefore resulting in an increase in the strength of the magnet and therefore attracting an increase in iron filings.

I can relate this to my prediction about the increase in current. I think that more current will affect the strength of the magnet; as the current is increased the more domains arrange in the same direction, this continues to occur until the core reaches saturation point and an increase in the current has little further effect. From my research the saturation point of an iron core is when all of the domains are of the same alignment. Although I have found from previous research that the core can often retain a small amount of magnetism when the current is stopped. This can effect the amount of iron filings that are attracted. Although, when this occurs, shocking or colliding the core against a hard surface can discharge it.

Method

In order to carry out the experiment the potential variables which could be altered, and their effects on the strength of the magnetic field must be identified they are:

The core material, the current, the Voltage, the coil density (size of wire), number of coils, the conductivity of the wire coil, the Core mass, the distance between the load and the electromagnet and the material of the Ferro magnetic coil.

All of the variables that I have written above I will keep the constant throughout the experiment will except for the current that I will be altering.

Despite this, there are other potential variables, which may alter the strength of the Electro-magnetic field, although to keep these constants would require a degree of accuracy that I cannot perform.

For this particular experiment I will be investigating the affect of current passed through the circuit, on the strength of an electromagnet.

I plan to create an experiment that changes the current that is passed through the circuit. The measurement of the strength of the electromagnet will be accessed by the mass of iron filings that the magnet will attract. This will then be weighed and the compared.

To do this I will construct an electromagnet by wrapping wire around an iron core to form a helix coil. I will connect this to a power pack that will also allow me to regulate the power of the magnet. I will also use an ammeter and a voltmeter and a variable resistor to obtain the desired amperes and voltage. Here are the instructions for constructing the experiment:

1. Wrap the insulated wire around the shaft of the core in a clockwise direction to form a helix wire coil.

2. Connect the power pack and variable resistor to the electromagnet this will give the correct sett

ing. 3. Plug the power pack into the main socket and turn on the

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power supply

4. Assure that the current and voltage is as desired, read from the voltmeter and ammeter.

5. Using the digital scales, weigh exactly 5 grams of iron filings.

6. Turn off the power supply and use a ruler to measure 10cm from the electromagnet and place 5 grams of iron filings at this distance.

7. Turn on the power supply.

8. Before turning off the power supply carefully lift the electromagnet and rest over a container.

9. Turn off the power supply.

10. Remove all of the iron filings collected in the container and weigh on the digital scales.

11. Record the results in a pre-made chart.

12. Remove the core from the wire coil and bang on a hard surface to remove any retained magnetism then repeat the experiment for each level of ampere (Starting at 1amps and increasing the amperes by 0.2amps each time until 2.6amps is reached).

This is a blue print of the circuit that should be constructed in order to carry out the experiment:

Equipment

Below is a list of all of the equipment that is essential requirements to carry out the experiment:

1x Iron nail (10cm in length)

Insulated copper wires (50 coils around the shaft of the nail)

1x Power pack

8x Connecting wires and crocodile clips (

1x Voltmeter

1x Ammeter

1x Variable resistor

1x Iron filings (150grams, enough to repeat the whole experiment three times)

1x Digital scales (Measurement of 2 decimal place accuracy)

Fair Test

To ensure that my test is as fair and non-biased as possible, I am going to keep all of the variables the same, except for current, which of course needs to change as this is the factor that is being investigated.

Also, to ensure accurate results, when measuring the iron filings I am going to use digital scales that supply information to 2 decimal places which I feel is an appropriate accuracy for the results that need to be obtained. To make my results even more accurate I am only altering one variable, the current by 0.2 every time.

In addition to this I am also going to ensure that the core will not retain any magnetism between each measurement by banging it against a hard surface. This will ensure that all of the domains in the iron core will arrange back to their original alignment.

To assure that the experiment is fair I used a preliminary experiment to determine at what distance to have the iron filings from the electromagnet. This will ensure that the electromagnet will not attract more or less iron filings that any other experiment.

To add even more accuracy to the experiment I used a voltmeter, ammeter and a variable resistor to ensure that the current and voltage is as desired.

Results:

SALT PERCENTAGE

TEST 1

TEST 2

AVERAGE

STARTING WEIGHT

ENDING WEIGHT

STARTING WEIGHT

ENDING WEIGHT

STARTING WEIGHT

ENDING WEIGHT

0

3.2

3.2

3.2

3.2

3.2

3.2

2

3.3

3.0

3.4

3.2

3.35

3.1

4

3.2

2.7

3

2.8

3.6

2.75

6

3.4

2.9

3.3

3.0

3.35

2.95

8

3.3

2.8

2.9

2.6

3.1

2.7

10

3.3

2.7

3.3

3.0

3.3

2.85

Conclusion

From analysing the results that have been produced I believe that it is easily visible to see that my prediction was correct.

The results show that there is a proportional relationship between current and the strength of the Electro-magnet (as predicted). I think this due to the domain theory Therefore this means that as one is increased then the other will increase. Using the results plotted on the graph can reinforce this. When the current passed through the wire a magnetic field was created along the axis of the wire coil. When the iron core was inserted into the wire coil, the magnetic field flowed in the direction of the axis, alters and arranged the domains within the iron to an attractive polarisation. It is due to this fact that the change of domains in polarisation greatly increases the strength of the magnet; therefore resulting in an increase in the strength of the magnet and therefore attracting an increase in iron filings.

When more current was applied the strength of the magnet increased this is shown in the results. This is because as the current is increased the more domains arrange in the same direction, this continues to occur until the core reaches saturation point and an increase in the current has little further effect.

From my research the saturation point of an iron core is when all of the domains are of the same alignment. Although I have found from previous research that the core can often retain a small amount of magnetism when the current is stopped. This effected the amount of iron filings that were attracted even after shocking and colliding the core against a hard surface to discharge it. This can be easily seen in the second experiment, the first measurement was not what was expected, it was more than the second measurement. This was because it must have retained some magnetism. This has effected the results and has created an anomalous outcome. This is unfortunate, as the average has been effected.

Evaluation

Overall, I feel that the methods that I used to gain the results were very accurate and fair, although if I wanted to improve the quality and the validity of the results I would possible conduct the experiment in a different way. I would allow myself an appropriate amount of time in which I would repeat the experiment to confirm any possible trends that may be found. By doing this any possible anomalous results would be eliminated and a more sound picture of the results could have been given. Although despite this I believe my investigation has been very successful. My original prediction was proven to be correct and I feel satisfied that the experiment enabled me to gather suitable data that allowed me to make a valid conclusion.

I have studied the graph and it was possible for me to identify some anomalous results. The most obvious one was in the first experiment at 1.8amps on the graph rises sharply and does not fit the line of best fit. I feel that this suggests this result is inaccurate. The result for 1.8amps from the second experiment confirms that the result was anomalous. The line of best fit for the average results (obtained from the mean average of the two experiments) represents an expected trend. The line is almost flat. I think that the graph would have been a perfectly straight line if the experiment were conducted in absolutely, perfectly controlled conditions. If I were to repeat my experiment I would increase the current until the saturation point of the core.

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