Physics
Electrostatics
Quick fact
The static charge from a doorknob shock can reach over 10,000 volts, but because the current is extremely low, it is usually harmless.
Why this is interesting
Ever wonder why a rubbed balloon sticks to a wall, or why you get a shock when touching a doorknob on a dry winter day? That invisible force is the magic of electrostatics—the study of stationary electric charges and the surprising effects they can create.
Read the full explanation
Understanding Electrostatics
Electrostatics deals with electric charges that are not moving—hence 'static.' Everything around us is made of atoms, which contain protons (positive charge) and electrons (negative charge). Usually, the charges are balanced, but when you rub a balloon on your hair, electrons transfer, leaving the balloon negatively charged and your hair positively charged. Opposite charges attract, so the balloon is attracted to the wall or your hair stands on end. The strength of the attraction depends on the amount of charge and the distance between objects, described by Coulomb's law: like charges repel, opposite charges attract. This force is one of the four fundamental forces in nature.
A deeper explanation
The underlying mechanism of electrostatics is the electric field, a region around a charged object where other charges feel a force. The field is a vector field that points away from positive charges and toward negative ones. The electric potential (voltage) describes the energy per unit charge at a point in the field. When charge builds up on an object, it creates a potential difference relative to its surroundings—if the difference becomes large enough, the charge can jump across an air gap as a spark. Electrostatic phenomena are crucial in technologies like photocopiers (toner is attracted to charged drum) and electrostatic precipitators (removing particles from smoke). Though static, these charges obey the same laws that govern electric currents—electrostatics is the foundation upon which our understanding of all electricity is built.