Finally, the phrase "scratch your skin off" is figurative. What does this phrase help the reader understand about the itch caused by a bedbug's bite?

The phrase helps the reader understand the extremity of the bug bite. By saying that your skin could essentially peel off, shows that with the bite you will have to scratch a lot. The force of scratching could feel like your skin is peeling off. Thus, the bug bite would be very bad and itchy.

Hope this helped :)

the direction of the magnetic field produced by an electric current will change when the direction of the electric current changes. for example : if a current is flowing in a straight length of wire, the magnetic field is described by a concentric circle (using right-hand rule).