An electric current is the rate of flow of electric charge past a point:2:622 or region.:614 An electric current is said to exist when there is a net flow of electric charge through a region.:832 In electric circuits this charge is often carried by electrons moving through a wire. It can also be carried by ions in an electrolyte, or by both ions and electrons such as in an ionized gas (plasma). The SI unit of electric current is the ampere , which is the flow of electric charge across a surface at the rate of one coulomb per second. The ampere (symbol: A) is an SI base unit:15 Electric current is measured using a device called an ammeter.
When a bunch of electrons congregate in one place, their combined charges build up to a certain level of electric potential energy in that object. For example, when I rub this rubber balloon on my wool scarf, it causes a bunch of the electrons from the scarf to jump over on the balloon. Now the balloon is negatively charged, because it has a surplus of negatively charged electrons, and the scarf is positively charged, because it has a shortage of electrons.