- #1
etotheipi
The EMF of the cell is the potential of the cathode subtract that of the anode, consistent with ##\Delta G = -nF\varepsilon##.
If the cell is running as a galvanic cell/discharging, the EMF should be positive. If it is charging, the cathode (the one gaining electrons) is now negative and at lower potential, so the EMF should be negative.
So if we draw a circuit diagram consisting of cells in different orientations, some should have positive EMFs and some should have negative EMFs. However, on circuit diagrams EMFs appear to always be labelled on cells as a positive value. Why is this?
There do exist some complications - if we don’t know the direction of current, then we also don’t know the sign of the EMF...
If the cell is running as a galvanic cell/discharging, the EMF should be positive. If it is charging, the cathode (the one gaining electrons) is now negative and at lower potential, so the EMF should be negative.
So if we draw a circuit diagram consisting of cells in different orientations, some should have positive EMFs and some should have negative EMFs. However, on circuit diagrams EMFs appear to always be labelled on cells as a positive value. Why is this?
There do exist some complications - if we don’t know the direction of current, then we also don’t know the sign of the EMF...