Problema Solution
A wire has a resistance of 20 ohms. It is melted down, and from the same volume of metal a new wire is made that is three times longer than the original wire. What is the resistance of the new wire?
Answer provided by our tutors
R=pL/s
When L'=3L, s'=s/3
So
R'=p(3L)/(s/3) = 9R = 180 ohms
So the resistance of the new wire is 180 ohms