Introduction

Electrostatics is the branch of physics that studies static (stationary) electric charges -- the forces they exert on each other, and the electric fields and electric potentials that surround them. Many of these ideas were touched on briefly in earlier standards; this chapter reviews and deepens that foundation before the next chapter (current electricity, produced by MOVING charges) builds directly on top of it.

Charges are present all around us at all times, though their effects usually only become noticeable under special circumstances. A very familiar example: on a dry winter day, pulling off a woollen sweater often produces a crackling sound, and the sweater seems to cling to the body -- this is the electric charge generated by friction between the sweater and the body. On a much larger scale, lightning in the sky during pre-monsoon weather is caused by an enormous quantity of electric charge that builds up on clouds, again due to friction (between rising and falling air/water/ice particles inside a storm cloud), and is then suddenly released. Both examples show the same underlying physics -- friction between two dissimilar materials can transfer charge from one to the other -- playing out at very different scales, from a single sweater to an entire thunderstorm.