Why is the northern kingdom, Israel, called Ephraim in Isaiah 7:2, 5, and 9? Webb suggests that it is because Jeroboam I, the first king of Israel, was an Ephraimite (1 Kings 11:26).
I just wanted to note this because people always get confused as they read through the Old Testament histories with so many variant names. For instance, Israel is Israel, all of it, sometimes. But sometimes it is the northern kingdom while Judah is the southern (but why isn't Benjamin mentioned when Judah is called Judah?). And so it goes.