Regarding Component tester socket in Oscilloscope

The oscilloscope at our basic electronics lab has a oscilloscope with component tester socket.Now when we insert a diode,resistor or zener diode it shows the respective V-I characteristics on the oscilloscope screen.
But when we checked a capacitor or inductor it showed an ellipse.
Can anyone comment on why ellipse is displayed on the CRO screen?

If you remember your circuit analysis, inductors and capacitors have the current and voltage out-of-phase (current leads the voltage for a capacitor and lags the voltage for an inductor). That generates the ellipse.

savvej said:

The oscilloscope at our basic electronics lab has a oscilloscope with component tester socket....

Click to expand...

It is called a "curve tracer". It basically plots current on the vertical axis vs voltage on the horizontal axis as voltage is swept from zero to +-max voltage. More advanced models include a current/voltage step generator synchronized with the voltage sweep, so that the transfer characteristics of Bipolar and Field Effect Transistors can be plotted.

Mike, I could be mistaken, but think he did mean component tester (like the Huntron Tracker 2800 and 2800S - Component level Troubleshooting for the benchtop,) rather than curve tracer.

OK, still a curve tracer: "The Huntron Tracker series of in-circuit component testers are specialized curve tracers. You could get the basic I-V plot for a component using a standard semiconductor curve tracer."