# Electrochemical cells a2

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Thread starter 3 years ago
#1
To calculate the electro potential of the cell, does the current have to be stopped from flowing?
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3 years ago
#2

The measured voltage will be lower due to the internal resistance of the cell: http://www.bbc.co.uk/bitesize/higher...ts/revision/3/
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Thread starter 3 years ago
#3
(Original post by Pigster)

The measured voltage will be lower due to the internal resistance of the cell: http://www.bbc.co.uk/bitesize/higher...ts/revision/3/
I don't take physics.. U mean this isn't included in A2 chemistry?
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3 years ago
#4
(Original post by pondsteps)
I don't take physics.. U mean this isn't included in A2 chemistry?
Internal resistance isn't a chemistry thing, it is deffo in the physics camp.

All chemists are interested in is the fact that the current should be zero, or at least as close as possible.
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3 years ago
#5
From what I remember you need a high resistance voltmeter, so there is a low current flow. (unless this is experimental) I don't think you need to worry about it, you can just use the values given
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Thread starter 3 years ago
#6
(Original post by Pigster)
Internal resistance isn't a chemistry thing, it is deffo in the physics camp.

All chemists are interested in is the fact that the current should be zero, or at least as close as possible.
Yeah that's was what I was trying to say actually !! Like should the current be zero to be able to find voltage
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3 years ago
#7
(Original post by pondsteps)
Yeah that's was what I was trying to say actually !! Like should the current be zero to be able to find voltage
The current that flows through the volt meter should be zero.

If you think of a potential as a measure of how much something wants to get from one place to another. (this is a very hand waving definition but it is useful).

Electrical potential (voltage) is a measure of how much a charged particle wants to go from one environment to another (eg between the anode and cathode of a battery). If you went to measure the voltage and you had a voltmeter of zero resistance, then as soon as you attatched the voltmeter across the cell, the electrons would travel through the voltmeter and that would change the potential you measured.

For example, with a rechargeable battery. If you had it fully charged, it would provide a potential, but, when it is fully discharged, all the electron have travelled round the circuit and ions have moved from one electrode to the other so that the potential is 0.

If you wanted to measure the difference in potential the battery could provide when fully charged, you obviously wouldn't choose a low resistance voltmeter, because this would provide a route for electrons to flow from one side of the battery to the other and so it would discharge the battery!

So yeah, the voltmeter should be high resistance because that way using it to measure the voltage shouldn't change the potential difference (voltage) you measure.
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