When you step on the brake pedal in your car, charge carriers flow from the batt

Question

When you step on the brake pedal in your car, charge carriers flow from the battery to the rear brake lights. Suppose the wire connecting the switch at the pedal to the brake lights is made of copper and has a diameter of 1.4 mm.

If the current through the wire is 2.0 A , how long on average does it take an electron to travel from the switch at the pedal to one of the brake lights? The number density of free electrons in copper is n = 8.4 x 1028 electrons/m3. Suppose that the length of the wire is 3 m.

Explanation / Answer

We know that, i= nAv(d)*e where, i:- current n:- number density of free electron v(d)= drift velocity of electron e= charge of electron.
A:- cross sectional area of wire.

A= Pi*(.7*10^(-3))^2= 1.53* 10^(-6) meter^2

So, v(d) = 0.097 * 10^(-3) m/s.

So time taken by electron= 3/(0.097 * 10^(-3)) = 30.92 *10^3 second.

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