In introductory electricity, what term describes the complete closed path along which an electric current flows?

In electrotherapy treatments, the term direct current (DC) refers to a current that:

In introductory electricity, what SI unit is used to measure the strength of an electric current?

In introductory electricity, electric current is measured in which SI unit?

Topic: Intro to Current. Two cylindrical copper wires have the same length but different diameters. Wire A has diameter $d_A$ and Wire B has diameter $d_B$, with $d_B>d_A$. If the same potential difference $V$ is applied across each wire, which wire can carry the higher current?

Topic: Intro to Current. For copper wire of the same length, which American Wire Gauge (AWG) will carry the most current before excessive heating (i.e., has the lowest resistance)?

In introductory circuit analysis, which wire gauge (American Wire Gauge, AWG) will typically carry the most current safely (all else equal, such as material and length)?

In introductory circuit analysis, which American Wire Gauge (AWG) wire can typically carry the most current (assuming the same material and similar insulation/ambient conditions)?

In an introductory circuits context, which device restricts electric current flow to a single direction?