Question

Two wires, one of magnesium and the other of copper, have equal lengths and resistances. Which one of these wires will be thicker?

Answer 1

• Resistance is the opposition to the flow of current.
• The formula for the resistance of a wire is $R=\frac{\rho l}{A}$, where $\rho$ is the resistivity, $l$ is the length, and $A$is the area of cross-section.
• Length $l$ and resistance $R$ of wires made up of magnesium and of copper are the same.
• Magnesium has a higher resistivity than copper.
• By rearranging the above equation we get, the area of the cross-section $A=\frac{\rho l}{R}$
• The area of the cross-section is directly proportional to the resistivity.
• Hence, the material magnesium which has higher resistivity will have a higher area of cross-section and will be thicker.

Final answer:

The wires made of magnesium will be thicker than copper wires.