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ponjavic
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Im a high-school student from Sweden currently competing in a worldwide physicstournament. Our task is to work with a problem both with theory and experiments. A professor here in Sweden told me that our problem is very similar to magnetoresistance.
The question is as follows:
Flow
Using a dc source, investigate how the resistance between two metallic wires dipped into a flowing liquid depends upon the speed and direction of the flow
The assignment consists of both building a theory revolving the connection between velocity, resistance and direction and also to prove these theories with experiments.
We have done some experiments and can conclude the following.
For water that runs in a U-shaped pipe solely accelerated by gravity:
If the electricity is led across the pipe the resistance grows with the velocity.
If the electricity is led alongsides the pipe the resistance grows or sinks with the velocity depending on the direction of the nodes in other words where we have - and +.
This is obviously unpure water as pure water would give no difference when switching - + and + - in the second scenario.
Certainly it seems as though scenario number one is the most normal and this on applies to magnetoresistance. We have an electric current and we apply a peripendicular force to it to change the resistance.
What I can conclude is that electricity in water is created by positive ions accepting electrons and negative ions releasing them e.g hydroxide and oxonium.
What I can't understand is why movement would negate some of these events. Why would a force change the resistance? Does it make the ions spend more energy? Do some ions not make it as far as to the electrode or what is it that happens?
I have no posibility (right now) to check wether pure water would change resistance when put through scenario one but I believe that it will. I also believe that it wouldn't change in scenario 2 because the number of + and - ions would be the same.
I was wondering if you could give us ideas on how to make formulas from magnetoresistance work for our case and also on how to conduct the experiments.
We started with the U-pipe by changing angles but we had big problems with that. We decided to have the pipe horizontally on the floor instead and by attaching the electrodes to a toy train or similar let them run through the water.
Any suggestions, theories or ideas on where we could find help, may you not be able, would be highly appreciated.
//Aleks Ponjavic
The question is as follows:
Flow
Using a dc source, investigate how the resistance between two metallic wires dipped into a flowing liquid depends upon the speed and direction of the flow
The assignment consists of both building a theory revolving the connection between velocity, resistance and direction and also to prove these theories with experiments.
We have done some experiments and can conclude the following.
For water that runs in a U-shaped pipe solely accelerated by gravity:
If the electricity is led across the pipe the resistance grows with the velocity.
If the electricity is led alongsides the pipe the resistance grows or sinks with the velocity depending on the direction of the nodes in other words where we have - and +.
This is obviously unpure water as pure water would give no difference when switching - + and + - in the second scenario.
Certainly it seems as though scenario number one is the most normal and this on applies to magnetoresistance. We have an electric current and we apply a peripendicular force to it to change the resistance.
What I can conclude is that electricity in water is created by positive ions accepting electrons and negative ions releasing them e.g hydroxide and oxonium.
What I can't understand is why movement would negate some of these events. Why would a force change the resistance? Does it make the ions spend more energy? Do some ions not make it as far as to the electrode or what is it that happens?
I have no posibility (right now) to check wether pure water would change resistance when put through scenario one but I believe that it will. I also believe that it wouldn't change in scenario 2 because the number of + and - ions would be the same.
I was wondering if you could give us ideas on how to make formulas from magnetoresistance work for our case and also on how to conduct the experiments.
We started with the U-pipe by changing angles but we had big problems with that. We decided to have the pipe horizontally on the floor instead and by attaching the electrodes to a toy train or similar let them run through the water.
Any suggestions, theories or ideas on where we could find help, may you not be able, would be highly appreciated.
//Aleks Ponjavic