Suppose you have a two wires. Each has a current of $5 \text{ A}$. One is made of copper (Cu) and has radius $0.5 \text{ mm}$. The other is made of zinc (Zn) and has radius $0.1 \text{ mm}$. What is the drift speed of electrons in each wire? You may want to consult the table below.

• The copper wire has $I=5 \text{ A}$, $r = 0.5 \text{ mm}$.
• The zinc wire has $I=5 \text{ A}$, $r = 0.1 \text{ mm}$.
• The charge of an electron is $q=-1.6\cdot 10^{-19} \text{ C}$.

• Drift speed for both wires.
• Electron charge density for both wires.
• Electron current for both wires.

• The table is accurate for our wires.
• The wires have circular cross-sections.
• The wires do not experience any external electric field.

• We represent electron current as $i=nAv_{avg}$.
• We represent current as $I=qi$. Current is charge per second. Electron current is electrons per second. We multiply by $q$ (the electron charge) to get charge per second.

We can look up electron