A rod has a square cross section with sides of length 2.0 cm. The current density in the rod , where is measured in meters, as shown in the diagram. Find the current through the face of the rod.
A 20 gauge wire has a cross-sectional area of 0.518 mm2. The current in the wire is modeled as , where is measured in seconds. What is the current density in the wire at the instant ?
An electron beam with a radius of 0.90 mm has a measured current . What is the magnitude of the current density of the beam?