What Is Static Charge?

A current can only flow as long as a potential difference is sustained; in other words, the flowing charge must be replenished. Therefore, some currents have a very short duration.

For example, a lightning bolt lasts only a fraction of a second, until the charge imbalance between the clouds and the ground is neutralized.When charge accumulates in one place, it is called static charge, because it is not moving.

The reason charge remains static is that it lacks a conducting pathway that enables it to flow toward its opposite charge. When we receive a shock from static electricity—for example, by touching a doorknob—our body is providing just such a pathway.

In this example, our body is charged through friction, often on a synthetic carpet, and this charge returns to the ground via the doorknob (the carpet only gives off electrons by rubbing, but does not allow them to flow back).

As our fingers approach the doorknob, the air in between is actually ionized momentarily, producing a tiny arc that causes the painful sensation.14 Static electricity occurs mostly in dry weather, since moisture on the surface of objects makes them sufficiently conductive to prevent accumulations of charge.

However startling and uncomfortable, static electricity encountered in everyday situations is harmless because the amount of charge available is so small,15 and it is not being replenished.

This is true despite the fact that very high voltages can be involved (recall that voltage is energy per charge), but these voltages drop instantaneously as soon as the contact is made.

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