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Question: The following questions refer to the circuit shown in Figure 18.114, consisting of two flashlight batteries and two Nichrome wires of different lengths and different thicknesses as shown (corresponding roughly to your own thick and thin Nichrome wires).

The thin wire is 50 cm long, and its diameter is 0.25 mm. The thick wire is 15 cm long, and its diameter is 0.35 mm. (a) The emf of each flashlight battery is 1.5 V. Determine the steady-state electric field inside each Nichrome wire. Remember that in the steady state you must satisfy both the current node rule and energy conservation. These two principles give you two equations for the two unknown fields. (b) The electron mobility

in room-temperature Nichrome is about $\mathbf{7}\mathbf{×}{\mathbf{10}}^{\mathbf{-}\mathbf{5}}\mathbf{}\raisebox{1ex}{$\left({\displaystyle \frac{m}{s}}\right)$}\!\left/ \!\raisebox{-1ex}{$\left({\displaystyle \frac{N}{s}}\right)$}\right.$. Show that it takes an electron 36 min to drift through the two Nichrome wires from location B to location A. (c) On the other hand, about how long did it take to establish the steady state when the circuit was first assembled? Give a very approximate numerical answer, not a precise one. (d) There are about $\mathbf{9}\mathbf{×}{\mathbf{10}}^{\mathbf{28}}$mobile electrons per cubic meter in Nichrome. How many electrons cross the junction between the two wires every second?

Step by step solution

01

Write the given data from the question.

The thin wire is 50 cm long and the diameter is 0.25 mm.

The flashlight battery is 1.5 V.

02

Determine the formulas

Write the formula for the drift speed of the electron.

03

Determine the time taken to obtain the steady state

Consider the electrical field is propagating the speed at .

Here, the shift of the electron sea takes very little time as the electron moves a very little distance. So the time taken to make a change of 0.5 m is 1.5 ns.

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