The electric field strength 32 cm from the surface of a 10cm

The electric field strength 3.2 cm from the surface of a 10-cm-diameter metal ball is 8.0 Times 10^4 N/C. What is the charge (in nC) on the ball? Express your answer to two significant figures and include the appropriate units.

Solution

E = kQ/r^2

k = 9*10^9

E = 8*10^4 N/C

r = distance from center = 3.2 + 5 = 8.2 cm

Q = E*r^2/k

Q = 8*10^4*0.082^2/(9*10^9) = 59.77 nC

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