Problem 18.56 A 5.70-m length of 1.8-mm-diameter wire carries a750 mA current wh
ID: 1424075 • Letter: P
Question
Problem 18.56
A 5.70-m length of 1.8-mm-diameter wire carries a750 mA current when 22.0 mV is applied to its ends.
Part A
Determine the resistance R of the wire.
Express your answer to two significant figures and include the appropriate units.
R =
Part B
Determine the resistivity .
Express your answer to two significant figures and include the appropriate units.
p =
Part C
If the drift speed is 1.7×105m/s, determine the number n of free electrons per unit volume.
Express your answer using two significant figures.
n =
Explanation / Answer
A) Resistance = R =V/I = 22*10^-3/750*10^-3 = 29.33 m-ohm
B) As R = L/A ==========> = RA/L = (29.33*10^-3*pi*0.9*0.9*10^-6)/5.7 = 1.31*10^-8 ohm-m
C) The number/unit volume of free electrons is given by: n = I/(vqA)
n = I/(vq((d/2)²) =0.75/[1.7*10^-5*1.6*10^-19*0.9*0.9*10^-6] = 3.404*10^29