An open-switch-path scan treats the open switch as a broken loop and varies the source voltage and load resistance across three rows, checking that the current stays I = 0 row by row. The arithmetic is exact only for the stated source voltages, load resistances, currents, and rows in the ideal switch, supply, and load model. Real circuits add contact resistance, leakage, finite rise time, supply tolerance, load impedance, probe/calibration limits, finite precision, and measurement uncertainty.
An open switch is not a conducting edge, so the loop current is zero. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.
highlighted = computed this step
An open switch breaks the path
When the switch is open, the conducting loop is broken at the switch.
open switch⇒no conducting loop
The current reading is zero
With no conducting path, the ammeter reads 0 amperes.
I=0A
Voltage does not matter without a path
The open switch blocks the branch in every row. Changing source voltage or load resistance does not create a conducting loop.