Asilver wire has a cross sectional area a = 2.0 mm2. a total of 9.4 × 1018 electrons pass through the wire in 3.0 s. the conduction electron density in silver is 5.8 × 1028 electrons/m3 and e = 1.60 × 10-19 c. what is the drift velocity of these electrons?

This problem uses the relationships among current I, current density J, and drift speed vd. We are given the total of electrons that pass through the wire in t = 3s and the area A, so we use the following equation to to find vd, from J and the known electron density n, so: 



The current I is any motion of charge from one region to another, so this is given by:



The magnitude of the current density is:



Being:



Finally, for the drift velocity magnitude vd, we find:



Notice: The current I is very high for this wire. The given values of the variables are a little bit odd

Full change in the electric plus system