Acertain laboratory experiment requires an aluminum wire of length of 30.0 m and a resistance of 3.80 ω at 20.0°c. what diameter wire must be used? (the resistivity of aluminum at 20.0°c is 2.82 ✕ 10−8 ω · m.)

diameter = 5.316 * 10^-4 meters

Explanation:
The resistance of the wire can be calculated using the following rule:
R = ΡL / A
where:
R is the resistance = 3.8 ohm
Ρ is the resistivity = 2.82 * 10^−8 ω · m
L is the length of the wire = 30 m
A is the area that we want to calculate
Substitute with the givens in the above equation to get the area as follows:
3.8 = (2.82 * 10^−8 * 30) / A
A = 2.22 * 10^-7 meters^2
Now, the area of the circle is calculated as follows:
Area = pi * (radius)^2
2.22 * 10^-7 = pi * (radius)^2
(radius)^2 = 7.066 * 10^-8
radius = 2.658 * 10^-4 meters
Diameter is double the radius. This means that:
diameter = 2 * 2.658 * 10^-4 = 5.316 * 10^-4 meters

Hope this helps :)

Julia would be observing a. static electricity was caused by her sweater rubbing against her shirt and transferring electrons. she didn't touch anything metal, so that would cancel out b.she most likely didn't rub her sweater against her hair either, so that cancels out c.she also didn't scoot across the carpet while trying to take her sweater off, that cancels out d.so that leaves a.a. is correct.