An iron-copper cell
The same rules work for any pair of metals. Take iron and copper in dilute sulphuric acid.
Figure to be added
Iron is above copper in the activity series. So the more reactive metal, iron, is the one that tends to be oxidised: it acts as the anode.
Fe (s) → Fe2+ (aq) + 2e
(4) at the iron — the anode reaction
Iron atoms go into solution leaving their electrons on the iron, which becomes negatively charged compared with the copper: the iron is the negative terminal. At the less reactive copper, the reduction half reaction happens, so copper is the cathode.
2H+ (aq) + 2e → H2 (g)
(5) at the copper — the cathode reaction
Electrons flow along the outside wire to the copper, so the copper is the positive terminal. Adding the half reactions gives the overall ionic reaction.
Fe (s) + 2H+ (aq) → Fe2+ (aq) + H2 (g)
(4) + (5)
What you would see
As the cell gives electricity, the iron electrode dissolves and gas bubbles come off the copper.
Why iron here and zinc before
Compare this cell with the zinc-copper cell. Copper is the cathode in both, and in both the cathode reaction is hydrogen ions gaining electrons. Only the anode has changed: the metal that dissolves is whichever of the two is higher in the activity series. Iron is lower than zinc, so an iron-copper cell pushes its electrons less strongly and gives a smaller voltage than a zinc-copper cell, but it works in exactly the same way.
Iron dissolves, copper bubbles
In an iron-copper cell, iron — higher in the series — is the anode and negative terminal; copper is the cathode and positive terminal.