Answer
See answers.
Work Step by Step
a. Treating the lake boundaries as equipotentials themselves, there are 6 contour lines between Iceberg Lake and Cecile Lake. From the figure caption, we see that differences between lines are interpreted as 80-volt differences, so there is a voltage difference is 640 V. Estimate the closest distance between the lakes to be 0.5 km.
The strength of the electric field is the change in voltage divided by the separation distance.
$$E=\frac{640V}{500m}\approx 1\frac{V}{m}$$
From the map, Iceberg Lake is at a lower elevation than Cecile Lake. The direction of the electric field is from high V to low V, so it points roughly up the page, slightly to the left. Your answers may vary.
b. Now consider the Minaret Mine. The direction of the electric field is from high V to low V, so it points roughly southeast there. Moving about 0.5 km to the southeast, one crosses about 5 contour lines, so the voltage changes by about 400 volts.
The strength of the electric field is the change in voltage divided by the separation distance.
$$E=\frac{400V}{500m}\approx 0.8\frac{V}{m}$$
Your answers may vary.
