Task: Text Categorization
Input (English): A more advanced form of this quantity is symbolized J and is called the density of this. In one case that density is equal to the permittivity of free space times the time derivative of the electric field. That case was introduced by Maxwell and is called the displacement of this quantity. One law states that its sum about at a junction is zero. It is measured by an ammeter (AM-ee-ter) and is equal to voltage divided by resistance according to Ohm's Law. This quantity is measured in amperes. For 10 points, name this rate of charge, which can be viewed as direct or alternating.
Output (English): Science