No 1. a) How long would a copper wire need to be if its resistance is one ohm an

Question

No 1. a) How long would a copper wire need to be if its resistance is one ohm and its b) How long would an iron wire need to be if its resistance is one ohm and it credit will be awarded for an answer without showing or explaining how you got it. Be sure to draw a picture. diameter is one half mm? diameter is one half mm? 2. a) A one mm diameter copper wire is connected to a 9-V battery in series wit an open switch; that is, the circuit is not complete. A break is made in the wir but the wire axis stays the same on both sides of the break, while a space of 0.1 mr is opened up. Then the switch is closed. What is the capacitance of these two wi segments? b) Reduce the opening of the above copper wire to 0.05 mm. Now what is t capacitance? c) Extra Credit: At what separation would an arc form across the opening?

Explanation / Answer

1) a) Given that

length of the wire is l = ?

R = 1 ohm

Radius is R = 0.5mm/2 = 0.25*10^-3 m

then
using

R = rho*l/A

rho is the resistivity of copper = 1.72*10^-8 ohm-m

then

R = rho*l/A

1 = (1.72*10^-8)*l/(3.142*(0.25*10^-3)^2)

l = 11.41 m

b) rho is the resistivity of Iron = 9.71*10^-8 ohm-m

then

R = rho*l/A

1 = 9.71*10^-8*l/(3.142*(0.25*10^-3)^2)

l = 2.02 m

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