It's important because you have to know when to make it go faster or else you might not be able to go upside down or in a circle
To get the charge along the inner cylinder, we use Gauss Law
E = d R1/2εo
For the outer cylinder the charge can be calculated using
E = d R2^2/2εoR1
where d is the charge density
Use these two equations to get the charge in between the cylinders and the capacitance between them.
Answer:
The time constant is 
Explanation:
From the question we are told that
the time take to charge is 
The mathematically representation for voltage potential of a capacitor at different time is

Where
is the time constant
is the potential of the capacitor when it is full
So the capacitor potential will be 100% when it is full thus
100% = 1
and from the question we are told that the at the given time the potential of the capacitor is 85% = 0.85 of its final potential so
V = 0.85
Hence



They are all coverd in water 24/7 they never clear up
I believe the answer is c but I’m not 100% sure