Question

Not too long ago houses were protected from excessive currents by fuses rather than circuit breakers. sometimes a fuse blew out and a replacement wasn't at hand. because a copper penny happens to have almost the same diameter as a fuse, some people replaced the fuse with a penny. unfortunately, a penny never blows out, no matter how large the current, and the use of pennies in fu se boxes caused many house fires. make the appropriate measurements on a penn y, then calcul ate the resistance between the two faces of a solid-copper penny. (modern pennies have the same dimensions, but are made of zinc with a copper coating.)

Answer 1

Answer: Resistance = $8.21 \times 10^{-8} \Omega$

The approximate diameter of a penny is, d = 20 mm

thickness of penny is, L = 1.5×$10^{-3}$ mm

The area of penny along circular face is,$A = \frac{\pi d^2}{4} =\frac{\pi (20 mm\frac{1 m}{1000 m})^2}{4}$

= 3.14×$10^{-4}$ m²

The resistivity of copper is ρ = 1.72 x 10-8 Ωm.

Resistance,

$R = \rho \frac{L}{A} = (1.72 \times 10^{-8} \Omega m)\frac{1.5 \times 10^{-3} m}{3.14 \times 10^{-4} m^2} = 8.21 \times 10^{-8} \Omega$