I have a little different opinion than your approach.
The rod is lowered to touch the bottom. It is vertical, not horizontal.
And are you sure no other quantities are given?
IMO, which doesn't actually counts, I think coulomb's law in applicable only to charges which are smaller than the distance between them.
And Coulomb's law is there in electrostatics. You might read more about magnetic field and forcehttp://electron9.phys.utk.edu/phys136d/modules/m7/magnetic.htm.
It could be like this. First you prove that something like √2 is irrational.
Then let, on contrary, √(√2) = p/q where p and q are co-prime
Square both sides, √2= p^2/q^2=(p/q)^2
But you know that the square of any fraction which contains co-prime can't be irrational or something with an under...
You might be interested in Joule's calorimeter experiments for deriving the Joule's Heating Law. Google for it.
And, yes, increase in temperature means less average relaxation time and hence more resistance.
In F=ma, the mass considered is of the object on which it is acting and the acceleration is also on the object on which it is acting. It is not about the mass and acceleration of force itself.
Consider this. A train is pulling coaches with constant acceleration. You need to calculate force...
When you have high resistors and you desire a lower resistance, you use this combination. (Only possible when you are working in junkyard or a 1200 AD lab)
Effective resistence helps you know the current passing through the junction. What if you were planning to attach an iron somewhere and you...