Answer
See the graph below.
Work Step by Step
We know that the electric filed is given by
$$E_s=-\dfrac{dV}{ds}$$
which is the negative slope of the $V$ versus $x$ graph.
We have here 3 stages which are:
- From $x=0$ cm to $x=10$ cm,
$$E_{x1}=-\dfrac{dV}{dx}=-\dfrac{-100- (-100)}{0.10-0}=\bf 0\;\rm V/m$$
- From $x=10$ cm to $x=20$ cm,
$$E_{x2}=-\dfrac{dV}{dx}=-\dfrac{100- (-100)}{0.20-0.10}=\bf -2000\;\rm V/m$$
- From $x=20$ cm to $x=40$ cm,
$$E_{x3}=-\dfrac{dV}{dx}=-\dfrac{100- 100}{0.40-0.20}=\bf 0\;\rm V/m$$
Now we can draw the $E_x$ versus $x$ graph, as we see below.
