Which solution is filled in a salt bridge?

$A$ variable,opposite external potential $(E_{ext})$ is applied to the cell $Zn | Zn^{2+} (1 \ M) || Cu^{2+} (1 \ M) | Cu$ of potential $1.1 \ V$. When $E_{ext} < 1.1 \ V$ and $E_{ext} > 1.1 \ V$,respectively,electrons flow from:

In the cell represented as $Ni_{(s)}|Ni_{(1M)}^{2+}||Ag_{(1M)}^{+}|Ag_{(s)}$,the reducing agent is

What is the change in oxidation number of $Pb$ at the positive electrode of a lead accumulator acting as a galvanic cell?

Give advantages of fuel cell.

One of the commonly used electrodes is the calomel electrode. Under which of the following categories does the calomel electrode fall?