During a thunderstorm, charge can become separated inside clouds. This creates a very large potential difference and a strong electric field between the cloud and the ground. The electric field becomes especially strong around pointed or raised objects such as trees, towers and masts. These objects can help an ionised path develop through the air. When the air breaks down electrically, a huge current can flow in a rapid discharge: lightning. Tall objects are therefore more likely to become part of the path, although lightning does not simply choose the nearest object every time. Lightning conductors provide a low-resistance route to the ground, helping to carry the current safely around a building.

This is also a design problem. Cameras, glasses, screens, road signs and medical scanners all depend on controlling how electromagnetic waves are emitted, absorbed, reflected or refracted. A familiar object can therefore be a practical example of the same wave rules studied in class.

At the microscopic level, the important particles are electrons. Moving electrons from one material to another leaves an imbalance of charge, and charged objects create electric fields around them. Those fields can attract or repel other charges without contact. In electronic sensors, very small changes in charge or capacitance can therefore be turned into a measurable electrical signal.