An iv curve is generated for two ohmic devices, one is a good conductor and the other is a good insulator. which one will have a lower slope?

As per the question there are two ohmic devices.

The first ohmic device is a good conductor and the second one is a good insulator.

As per Ohm's law the current flowing through a conductor is directly proportional to the potential difference maintained across the two ends of a conductor at constant temperature and pressure. If V is the potential and I is the current flow through these Ohmic devices,then mathematically it can be written as-

                                                      V∝ I   [ at constant temperature and pressure]

                                                   ⇒V= IR

Here R is the proportionality constant called resistance of the material.

 Hence the resistance R  is calculated as -

Now a graph is plotted taking potential  V on X-axis and current I along Y- axis.

The graph will be a straight line  for conductor and will be a curve depending on the type of insulator.

The slope of this graph will give  the resistance of the material.

An insulator is a substance through which current flow is very low as its resistance is very high.Hence the slope of the V-I curve is very large.

A conductor is that substance through which current is flown easily as  the resistance of conductor is very low.Hence the slope of V-I curve is smaller,

think its the third option