Question

A point charge q1 = 3.75 nC is located on the x-axis at x = 1.80 mm , and a second point charge q2 = -6.35 nC is on the y-axis at y = 1.05 m

a) What is the total electric flux due to these two point charges through a spherical surface centred at the origin and with radius r1 = 0.390 m

b)What is the total electric flux due to these two point charges through a spherical surface centred at the origin and with radius r2 = 1.55 mm

c)

What is the total electric flux due to these two point charges through a spherical surface centred at the origin and with radius r3r3r_3 = 2.85 m

Answer 1

Electric flux is given by:

= 8.85*10^-12

Qnet = Net electric charge inside spherical surface

Part A.

When radius of spherical surface r1 = 0.390 m

then both charge q1 and q2 will be out of the spherical surface, since both x & y > r1, So

Qnet = net charge inside spherical surface of radius r1 = 0

Which gives

Part B.

When radius of spherical surface r2 = 1.55 m

then charge q1 is outside the surface and charge q2 is inside the spherical surface, since x > r2 & y < r2

Qnet = net charge inside spherical surface of radius r2 = q2 = -6.35 nC = -6.35*10^-9 C

Which gives

(-6.35*10^-9)/(8.85*10^-12)

-717.51 N.m^2/C

Part C.

When radius of spherical surface r3 = 2.85 m

then both charge q1 and q2 will be inside of the spherical surface, since both x & y < r1, So

Qnet = net charge inside spherical surface of radius r3 = q1 + q2 = 3.75 nC - 6.35 C = -2.6 nC = -2.6*10^-9 C

Which gives

(-2.6*10^-9)/(8.85*10^-12)

-293.78 N.m^2/C