My Question:

Draw V-I Graph for both ohmic and non-ohmic materials stating one example of each as well.

thanks!

Let's begin with the Ohm's Law

It states that the amount of current (I) flowing through a material (say a wire) is directly proportional to the voltage (V) applied across its ends. Mathematically, it is given as

V ∝ I

or

V = RI

here R is a constant of proportionality also known as the resistance. So, the resistance of a material following the Ohm's Law will always stay constant for all values of external voltage applied.

Now, using this principle, we can distinguish materials as either being Ohmic or Non-Ohmic in nature. Such that,

Ohmic materials follow the Ohms' law as the resistance remains unaffected even if we change the applied voltage (which alters amount of current flowing).

The V-I graph in this case shows a linear trend, as follows

A few examples include Nickel, Copper etc. 

Non-Ohmic materials, as the name suggests, do not obey the Ohm's Law in its strictest sense as the resistance varies with applied voltage.

The V-I graph in this case would show a gradual curved slope, as follows

A few examples include Thermistor, Diode etc.