[ilovemath]

a salt bridge is used in a voltaic cell. it seems that it is VITAL for the circuit to work

I don't see how the salt bridge is needed for electron flow??

indeed I though electrons DID NOT flow in voltaic cells.
I thought a voltaic cell simply measured the pd between two half cells??

[charco]

(Original post by ilovemath)
a salt bridge is used in a voltaic cell. it seems that it is VITAL for the circuit to work

I don't see how the salt bridge is needed for electron flow??

indeed I though electrons DID NOT flow in voltaic cells.
I thought a voltaic cell simply measured the pd between two half cells??

There is no actual flow while a high resistance voltmeter is in place, but of course, once it's removed then current would flow.

However, the voltmeter measures the difference between the pull on the electrons in one half cell and the push of electrons in the other.

Were there no salt bridge, there could be no equalising movement of ions, which prevents the build up of charge in the half cells. Any charge build-up immediately prevents the push/pull effect.

[ilovemath]

(Original post by charco)
There is no actual flow while a high resistance voltmeter is in place, but of course, once it's removed then current would flow.

However, the voltmeter measures the difference between the pull on the electrons in one half cell and the push of electrons in the other.

Were there no salt bridge, there could be no equalising movement of ions, which prevents the build up of charge in the half cells. Any charge build-up immediately prevents the push/pull effect.

is this because:
the left cell produces cations and so becomes +ve and the right cell removes cations become -ive??

and do charges flow at other times because:
the left electrode has a greater ive charge as metal gives up electrons more easily so they flow to the next electrode to balance the charges??

If so surely, after some time, the electrons should stop flowing when the electrons in both systems are balanced???

[ilovemath]

of course!!
at the other electrode they recombine with the metal ion to form the metal