Question

Your mother is using an electric flat iron that draws a current of 15 A when connected to a 220 V line.

(a) What is the resistance of the heating element of the flat iron assuming that it obeys Ohm’s law? What is the resistivity of the heating element if it is a wire that is 2.7 cm long with a cross-sectional area of 2.1 x 10^-4 m²?

Answer 1

(a)

$$R=\frac{V}{I}=\frac{220}{15}=14.7\:\Omega$$

(b)

$$\rho=\frac{RA}{l}=\frac{14.7*2.1*10^{-4}}{0.027}=0.11\:\rm \Omega\cdot m$$