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a) A disk of radius a = 22.7 cm lies in the yz plane with its axis along the x-a

ID: 1638014 • Letter: A

Question

a) A disk of radius a = 22.7 cm lies in the yz plane with its axis along the x-axis and carries a uniform surface charge density rho = 3.8 nC/m^2. Find the value of x for which Ex = 107.3 N/C.

b) In a particular region of the Earth's atmosphere, the electric field above the Earth's surface has been measured to be 147 N/C downward at an altitude of 245 m and 166 N/C downward at an altitude of 401 m. Calculate the volume charge density of the atmosphere assuming it to be uniform between 245 and 401 m. Neglect the curvature of the Earth

Explanation / Answer

Not sure about (a)

b)

= volume charge density of the atmosphere

= 8.854 x 10^-12 C^2N^-1m^-2

E1 = 147 N/C, h1 = 245 m

E2 = 166 N/C, h2 = 401 m

According to Gauss Law:

E*dS = Q/

E*dS = S(E1 - E2)

Q/ = V/ = S(h2 - h1) /

S(E1 - E2) = S(h2 - h1) /

E1 - E2 = (h2 - h1) /

= (E1 - E2) / (h2 - h1)

= (8.854 x 10^-12)*(147 - 166) / (401 - 245)

= -1.078 x 10^-12 C/m^3