Principle

A lightning forms a strong electric current, which is created, when in a medium (for example air) a large number of free charges is produced by strong electric fields. During a thunderstorm usually high elevations from earth (for example skyscrapers) are more often affected by lightning strokes.
Investigate how the electric field between a thundercloud and the earth ground is distributed in the area next to a skyscraper. Consider the thundercloud and the ground as parallel electrodes. Simulating a high building one of the electrodes will be configured with a sharp elevation.

Benefits

• No electrolyte required
• Direct measurement of potential with high resistance voltmeter
• Measuring points can be transferred (pressed through) onto a sheet of white paper during measurement

Tasks

1. Measure the distribution of the potential within the electric field and derive the electric field pattern.
2. Observe how the electric field changes in the area of the tip electrode and transfer your observations to the situation of a thunderstorm.

Learning objectives

With this experiment the students will investigate how a lightning is created during a thunderstorm and why elevations from the earth such as skyscrapers have a higher risk of being struck. In the experiment the students will simulate the electric field between a thundercloud and the earth ground by two parallel rod electrodes. One of the electrodes contains a tip-shape electrode, which changes the homogeneous electric field the same way a skyscraper will change the field between thundercloud and earth ground.