Final answer:
Contour lines close together on a topographic map signify that the slope is steep.
Step-by-step explanation:
Contour lines that are close together indicate the slope is steep. The analogy given here is between electric potential and gravitational potential on a topographic map. Similar to how isolines of electric potential getting closer together signify a stronger electric field, isolines of gravitational potential getting closer together on a topographic map signify a steeper slope on a hill. Therefore, if the isolines of gravitational potential on a topographic map are close together, then the hill will have a steeper slope.