By using Ohm's law, we can find what should be the resistance of the wire, R:

Then, let's find the cross-sectional area of the wire. Its radius is half the diameter,

So the area is

And by using the resistivity of the Aluminum,

, we can use the relationship between resistance R and resistivity:

to find L, the length of the wire:
Answer: 
Explanation:
Given
Diameter of the rod 
length of rod is 
Resistivity of silicon is 
cross-section of the rod 

Resistance of rod is R


Current is given by

Answer:
Since the ball becomes positively charged, it will repel as like charges repel.
This is a question that would have literally have taken two seconds to look up on google but the answer is 1.88 years.
Answer:
potential energy is a type of energy an object has because of it's position