When using the R x 100 range to test an N channel JFET, what should be the readings between source and drain?

When testing an N channel JFET with the R x 100 range, the expected readings between the source and drain terminals should be equal in both directions. This is a characteristic of the JFET when it is in the off state, as it behaves as a high resistance device at this point.

In an N channel JFET, the current primarily flows from the drain to the source when the gate-source junction is reverse-biased (which is the typical scenario during testing). When the JFET is not conducting, the resistance should ideally be very high, leading to similar high resistance measurements in both directions. The equal readings indicate that the junctions (drain-source and gate) are functioning properly without any shorts or unexpected conduction paths.

Other options are not reflective of the expected behavior of an N channel JFET. Higher or lower readings in one direction would suggest asymmetrical behavior or damage, indicating a potential fault in the JFET. Fluctuating readings could imply issues with the tester, unstable connections, or operational anomalies in the device itself. Therefore, the rationale for expecting equal readings in both directions during this test is rooted in the fundamental operation principles of JFETs.