ECE106 Lecture Notes - Lecture 60: Electric Current, Qi, Electric Field

• School: University of Waterloo
• Department: Electrical and Computer Engineering
• Course: ECE106
• Professor: All

Document Summary

Electric current in static case (time independent or dc) is defined as. For a time dependent situation (dynamic case), second dq dt i = s (7. 1) (7. 2) (7. 3) Note: dynamic current and ac current are not the same. Ac is a special case of dynamic current that involves only periodic oscillating change with time, which leads to frequency idea. Current (i or i) is a scalar quantity, while current density (j ) is a vector concept and it gives us the microscopic model of the rate of flow of charge. Figure 7. 1: current through different cross section: for area a1, i = ja or j = i where j = |j | Direction of j is defined as the direction in which a positive charge (if available) will move. Figure 7. 2: moving a negative charge is equal to moving a costive charge in opposite direction.