Introduction

Everyday Encounters with Static Electricity

Most of us have felt a small shock or heard a crackle while taking off a synthetic sweater or clothing, especially in dry weather — have you ever wondered why? A related, larger-scale example is the lightning we see in the sky during a thunderstorm. Even something as ordinary as opening a car door, or holding the iron handrail of a bus after sliding across the seat, can give you a mild electric shock.

Why This Happens

In each case, the shock or spark you feel is a discharge of electric charge through your body. This charge built up earlier — accumulated by the rubbing of insulating surfaces (your clothes against your body, or your body against the seat). This buildup of charge on a surface is what we commonly call static electricity. The word static simply means something that does not move or change with time.

What This Chapter (and the Next) Is About

Electrostatics is the branch of physics that studies the forces, electric fields, and electric potentials that arise from charges at rest — precisely the phenomenon behind all the everyday experiences above. This chapter, and the one that follows, build up the ideas needed to understand and calculate these effects.