Voltage between two points of a square contour in a magnetic field
The law about induction speaks about a closed path around a magnetic field, but using conductive material, you should think of a small gap in the path. The voltage can be measured at this gap, see left sketch:







simulate this circuit &ndash; Schematic created using CircuitLab

If there's no gap and the wire is a superconductor (Rs=0), you have a short circuit. Current will flow, but you will not measure any voltage anywhere. (Well, things happen then...)

In reality, the wire has a resistance. Calculate the induced voltage, and via the resistance, you get the current flowing. This is sketched in the right figure. As you can already see, the voltage measured between the two legs should be half the supply/induced voltage.