# Electrical Resistance The resistance R of a wire variesdirectly as its length L and inversely as the square of itsdiameter d.(a) Write an equation that expresses this joint variation.(b) Find the constant of proportionality if a wire 1.2 mlong and 0.005 m in diameter has a resistance of140 ohms.(c) Find the resistance of a wire made of the same materialthat is 3 m long and has a diameter of 0.008 m.(d) If the diameter is doubled and the length is tripled, bywhat factor is the resistance changed?

Question

Electrical Resistance The resistance R of a wire varies
directly as its length L and inversely as the square of its
diameter d.
(a) Write an equation that expresses this joint variation.
(b) Find the constant of proportionality if a wire 1.2 m
long and 0.005 m in diameter has a resistance of
140 ohms.
(c) Find the resistance of a wire made of the same material
that is 3 m long and has a diameter of 0.008 m.
(d) If the diameter is doubled and the length is tripled, by
what factor is the resistance changed?