An iron wire has length 8.0 m and diameter 0.50 mm. The wire has resistance R.
A second iron wire has length 2.0 m and diameter 1.0 mm.
What is the resistance of the second wire?

the answer is R\16 how do we figuire it out ?

Question

An iron wire has length 8.0 m and diameter 0.50 mm. The wire has resistance R.
A second iron wire has length 2.0 m and diameter 1.0 mm.
What is the resistance of the second wire?


the answer is R\16 how do we figuire it out ?

anonymous · Answer

Key: Both the wires are made up of Iron. So their resistivity is same.
Resistivity = $$Resistivity, \rho  = resistance (R) \times area (A) / length (l)$$ 
Calculate resistivity for both the wires, put them equal to each other and solve for the resistance of the second wire.