The resistance of a wire of $0.01 cm$ radius is 7 ohms. If the resistivity of the material of the wire is $44 \times 10^{-6} ohm$ meter, calculate the length of the wire.

Given: Radius of the wire = 0.01 cm = 0.0001 m, Resistance of the wire = 7 ohms, Resistivity of the material of the wire = 44 x 10^-6 ohm meter.

We know that, Resistivity = Resistance x Area / Length

or, Length = Resistance x Area / Resistivity

= 7 ohms x π x (0.0001 m)^2 / (44 x 10^-6 ohm meter)

= 0.05 m