1. A wire has a cross-sectional area of 5.5×10-6 m2. In a time of 3.7 s, 5.8 C of charge flows through it. What is the magnitude of the current density in the wire?
2. The solar wind consists of particles, including protons, that flow outward from the Sun. Near the Earth, the density of protons in the solar wind is 8.72×10-6 protons/cm3, speeding through space at 475 km/s. What is the magnitude of the current density of protons near the Earth?