What is the surface charge density on the sphere of radius 7.1? Express your ans

Question

What is the surface charge density on the sphere of radius 7.1? Express your answer using two significant figures Two spheres with uniform surface charge density, one with a radius of 7.1 cm and the other with a radius of 5.0 cm, are separated by a center-to- center distance of 38 cm. The spheres have a combined charge of +55HC and repel one another with a force of 0.70 N. Assume that the charge of the first sphere is greater than the charge of the second sphere. C/m2 Submit Previous Answers Request Answer Incorrect, Try Again; 8 attempts remaining Part B What is the surface charge density on the second sphere? Express your answer using two significant figures 2 = C/

Explanation / Answer

charge on sphere1 = q1

charge on sphere 2 = q2

q1 + q2 = 55*10^-6 C

q2 = 55*10^-6 - q1 ........(1)

electrostatic force of repulsion F = k*q1*q2/r^2 = 0.7

9*10^9*q1*q2/0.38^2 = 0.7

q1*q2 = 1.12*10^-11 .......(2)

using 1 in 2

q1*(55*10^-6 - q1) = 1.12*10^-11

q1 = 54.8 uC

q2 = 0.2 uC

part A

charge density sigma1 = q1/(4*pi*r1^2) = 54.8*10^-6/(4*pi*0.071^2) = 865*10^-6 C/m^2

part B

charge density sigma2 = q2/(4*pi*r2^2) = 0.2*10^-6/(4*pi*0.05^2) = 6.37*10^-6 C/m^2

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