Phys 1112 Research report Write a report about the dielectric breakdown of air,

Question

Phys 1112 Research report Write a report about the dielectric breakdown of air, then use the knowledge you gained to answer the following questions A positively charged powder of charge density p 2.4 x 10-3C/m3 is being dropped into a pipe of radius 5 cm and it end at a flat surface as shown in the figure below. 1- Air Earth surface the powder is moving down in the pipe at constant speed of v 3.2 m/s and it takes 8 s to see a discharge lightning from the circular disc toward the earth. (a) Find the total charge q stored on the circular disc before the discharging. (b) Modeling the case as a parallel plate capacitor with a circular disc as an upper plate and the piece of Earth that facing the disc as the bottom plate, find the area A of each plate.

Explanation / Answer

From the given diagram

1. charge density of +vely charged powder is rho = 2.4*10^-3 C/m^3

radius of pipe, r = 0.05 m

spee dof powder, v = 3.2 m/s

time taken to see discharge, t = 8 s

a. at t = 8 s

charge stored on disc = rho*v*t*pi*r^2 = 4.82548*10^-4 C

b. modelling the case as parallel plate capacitor

let radius of each plate be A

now, dielectric breakdown of air happens at E = 3*10^6 V/m

hence

for plate seperation d

Capacitance = A*epsilon/d ( where epsilon is permittivity of air)

also, Q = CV

and

E = V/d

hence

Q = CEd

Q = A*epsilon*E

A = Q/epsilon*E = 4*pi*k*Q/E = 18.1512289324610 m^2

Related Questions

Navigate

• Browse (All)
• Browse P
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.