double lines between anode and cathode

[Shannon Wasley 2J]

Are the double lines between the anode and cathode always used, or is there any situation where the cell diagram would not have the double lines?

[Sabrina Fardeheb 2B]

It is always used to separate the cathode and anode. It represents the salt bridge.

[Brigitte Phung 1F]

The double lines represent the salt bridge in galvanic cells. The elements to the left of the double lines represent the anode/oxidation reaction, while the elements to the right of the double lines represent the cathode/reduction reaction.

[Sirajbir Sodhi 2K]

In a galvanic cell, the purpose of a salt bridge is to maintain the charges in the anode and cathode so the reaction can continue while ensuring that half-cells do not mix (if they did mix, they would directly oxidize/reduce the other, electrons wouldn't pass through a wire, no work would be done).

A salt bridge doesn't have to be used when either one of the following occurs:
1. a porous barrier is used in a galvanic cell (basically serves the same function as a salt bridge).
2. electrolysis is occurring, meaning that the oxidation/reduction reaction is not spontaneous so it doesn't matter if the half-cells mix because nothing will happen without a current.