• Join over 1.2 million students every month
• Accelerate your learning by 29%
• Unlimited access from just £6.99 per month

# Assess the effect length on the resistance of brine soaked paper

Extracts from this document...

Introduction

Physics Coursework

## Plan

In this project, I am trying to assess the effect length on the resistance of brine soaked paper.

To do this, I am attempting to measure the current flowing through a circuit with the paper in.

In order to start the experiment, I will need the following apparatus:-

 Milli-ammeter Voltmeter Power Pack 2 Retort Stands + Clamps Glass Paper 2 Bull-dog Clips 2M Brine Solution Connection Wires 2 Crocodile Clips

Here is a circuit diagram of the proposed experiment: Here is a diagram of how the retort stand will be arranged: ## Preliminary

Before starting my main experiment, I performed a preliminary experiment that helped me to determine what unforeseen obstacles or difficulties I would encounter:

1. I found that the paper becomes too fragile to handle when it is over 30cm long. It breaks when soaked in water.
2. I found that water stays evenly soaked onto the paper when it is clamped in a horizontal position
3. I found that the saline solution causes salty deposits to be left on the Bull-dog clips.
4. I found that high voltages are detrimental to the experiment as they decrease the readings to quickly due to electrolysis. The experiment has to be carried out quickly and efficiently or the too much of the brine will ionise.
5. I found that rust occurs on the bull-dog clips that has to be sanded off between tests, to keep the readings accurate and the electrode clean. – An extra material I will need is sand-paper.

Middle

0.84

0.00084

8333

8

1.00

0.00100

8000

8419

30

5

0.50

0.00050

10000

6

0.61

0.00061

9836

7

0.73

0.00073

9589

8

0.87

0.00087

9195

9655 The graph shows that length is directly proportional to resistance, which is what I had previously predicted. This means that as length increases, resistance also increases at the same rate.

## Extension

I am going to extend the experiment by determining how paper width and concentration of brine solution effect resitance.

Width:

The experiment will be the same, except that the length will remain a constant, while the width will become the variable. I am using 1,2,3,4 and 5cm width measurements to test this.

Due to my previous work using copper wire to measure resistance, I found that the thicker the wire, the proportionally smaller the resistance is.

For this experiment - I predict that as the width increases the resistance will decrease inversely.

Here are the results I collected:

 Width (cm)  Potential difference (Volts) MAmps Amps Resistance (       ) Average 1 5 0.28 0.00028 17857 6 0.34 0.00034 17647 7 0.40 0.00040 17500 8 0.52 0.00052 15385 17097 2 5 0.60 0.00060 8333 6 0.75 0.00075 8000 7 0.9 0.00090 7778 8 1.13 0.00113 7080 7798 3 5 0.89 0.00089 5618 6 1.12 0.00112 5357 7 1.35 0.00135 5185 8 1.63 0.00163 4908 5267 4 5 1.16 0.00116 4310 6 1.42 0.00142 4225 7 1.76 0.00176 3977 8 2.08 0.00208 3846 4090 5 5 1.53 0.00153 3268 6 1.91 0.00191 3141 7 2.29 0.00229 3057 8 2.84 0.00284 2817 3071 The graph shows that width decreases inversely to resistance, which is what I had previously predicted. This means that as width increases, resistance decreases at a faster rate.

Concentration:

The experiment will be the same, except that the width will remain a constant, while the concentration of the brine solution will become the variable. I am going to use 0.05, 0.1, 0.2, 0.3, 0.4, 0.5M solutions to test it.

Conclusion

These agree with my predictions, although I did not predict 1/width and 1/concentration.

From these results, I can safely assume that:

Width    X    Thickness    =    Area                        ➔ Resistance is directly proportional to 1/area.

Using a constant to simplify and using a combination of rules I can say that:-

Resistance    =   Constant    X    Length➔ R   =         C L

Area                                                      A

I after researching what I could about electricity, I found that this equation was similar to that of resistivity. Resistivity is measured in ohm meters and is a constant value for a given material; the resistance of a unit length of the material per unit cross-sectional area. I can re-arrange the above equation so I can calculate resistivity:

 R = Resistance A = Area L = Length P = Constant

R A = p l        R A  = P                ➔ P = R A

## Evaluation

Most of my points were on or very close to the line of best fit, and so my results were reliable and demonstrate the connection between the variables we were testing. We could have used lower voltages using more sensitive equipment – to minimise the electrolysis taking place and could have collected more results although this would not have been worthwhile due to the minor accuracy advantage.

We did our experiments over a period of days so a temperature change could have occurred, but the effect of this is negligible. The stock solution used for the brine may not have been the same and may have differed (also to a negligible effect) slightly due to evaporation.

For extension work, I would try and find an equation that would allow me to acquire readings without the practical experiment.

This student written piece of work is one of many that can be found in our AS and A Level Electrical & Thermal Physics section.

## Found what you're looking for?

• Start learning 29% faster today
• 150,000+ documents available
• Just £6.99 a month

Not the one? Search for your essay title...
• Join over 1.2 million students every month
• Accelerate your learning by 29%
• Unlimited access from just £6.99 per month

# Related AS and A Level Electrical & Thermal Physics essays

1.  ## Measurement of the resistivity of Nichrome

5 star(s)

Graph B (Wire B) Max +2.7% +1.5% Min -2.7% -1.5% Add a straight line at both sides of the best fit line. Those lines should be inside any three error bars. Work out their gradients. Gradient calculation The data in the table below is in 3 decimal place Graph A (Wire A)

2.  ## Investgating resistivity - Planning and Implementing

4 star(s)

Diameter is measured to the nearest 0.005 mm, so it is given in millimetres to two decimal places. Significant sources of error The length of wire, current and voltage, and the wire's diameter are measured. The length of the wire has the smallest error, as the smallest value is 0.1m, and it is measured to the nearest millimetre.

1. ## Thermistor Coursework

This would mean using a graph for the sensor showing what the potential difference across the thermistor is at certain temperatures. Now that I have performed various calculations and an experiment, I can give the sensor and its details about the sensor the plant growing company.

2. ## Finding the Resistivity of a Wire

The measurement of diameter was my most error sensitive measurement, as it had to be halved and then squared to find the area of the cross-section of the wire.

1. ## Investigation On The Resistivity Of Apples. Since we are measuring the resistance of an ...

This may shorten the length measured so its resistance will decrease. 7. Measurement error associated with the ruler, such as not reading the markings on the ruler correctly. 8. As the different lengths of apple all have the same cross-sectional area, their surface area to volume ration will be different.

2. ## Investigating the effect of 'length' on the resistance of a wire

One volt of p.d is equal to one joule of energy per coulomb of charge. The term 'potential difference' is used for the voltage between two points in a circuit. If you increase the voltage then more current will flow.

1. ## Sensors Project Report

That means that the resolution of the sensor is 1 sheet. The error of the experiment 1. The reading may not be accurate enough because the voltage that was shown in the multimeters has great fluctuation 2. There is some resistance in the wires and internal resistance in the battery which will affect the result of the experiment.

2. ## Investigating the Smoothing Effect of a Capacitor on a Resistive Load

The Y-sensitivity on the CRO could be changed so that an enlarged ripple trace would be displayed for greater convenience in measuring the ripple voltage and reducing the significance of errors in reading off the CRO. The evidence from the results of this experiment I think proves to be quite • Over 160,000 pieces
of student written work
• Annotated by
experienced teachers
• Ideas and feedback to 