A very long cylinder of radius 2.60 cm carries a uniform charge density of 2.50
ID: 1330121 • Letter: A
Question
A very long cylinder of radius 2.60 cm carries a uniform charge density of 2.50 nC/m .
part A: Taking the reference level for the zero of potential to be the surface of the cylinder, find the radius of equipotential surfaces having potentials of 12.0 V .
Part B: Taking the reference level for the zero of potential to be the surface of the cylinder, find the radius of equipotential surfaces having potentials of 24.0 V .
Part C:Taking the reference level for the zero of potential to be the surface of the cylinder, find the radius of equipotential surfaces having potentials of 36.0 V .
Explanation / Answer
Va - vb = E * dr
Lower limit: a
Upper limit: b
= 2.50 nC/m
I have solved, using Gauss' Law, the electric field of this cylinder.
E = /(20)(r)
Now to integrate, I removed the /(20) factor out of the integrand and did this:
Vr - V.026 = /(20) * (1/r)dr
Lower limit for this integral: r (the distance from the axis of the cylinder)
Upper limit for this integral: 2.60 cm (the radius of the cylinder)
So Vr - V.026 = Vr =(/(20) * ln(.026/r)
If V.026 = 12
Vr = ((2.5 * 10-9) /(2**8.85*10-12)) * ln(0.026/x) + 12
Vr = 3.3954 cm
If V.026 = 24
Vr = ((2.5 * 10-9) /(2**8.85*10-12)) * ln(0.026/x) + 24
Vr = 4.43 cm
If V.026 = 36
Vr = ((2.5 * 10-9) /(2**8.85*10-12)) * ln(0.026/x) + 36
Vr = 5.79 cm