An electric heater is plugged into a wall socket by a flex whose copper conductors…

PHYSICS · Multi-part · Fermi University Physics · Electricity, Magnetism & Electromagnetism · Electric current and circuits · Electric current and circuits

Electricity, Magnetism and Electromagnetism, Ch Current, current density, conductivity and Ohm's law

Problem

An electric heater is plugged into a wall socket by a flex whose copper conductors each have a cross-sectional area of

1.5\,\mathrm{mm^2}

, and it draws a steady current of

13\,\mathrm{A}

. In copper the number density of conduction electrons is

n = 8.5\times10^{28}\,\mathrm{m^{-3}}

, and each carries a charge of magnitude

e = 1.602\times10^{-19}\,\mathrm{C}

. Take the current density to be uniform over the cross-section. ((a)) Estimate the drift speed of the conduction electrons in the flex. ((b)) The socket is

2.5\,\mathrm{m}

of flex away from the heater. Estimate how long a given electron takes to drift that distance, and comment on whether the electrons that leave the socket when the heater is switched on can be the ones that warm the element.

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