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Question
Careful measurement of the electric field at the surface of a black box indicates that the net outward flux through the surface of the box is 8.0 × 103 N m2/C.
- What is the net charge inside the box?
- If the net outward flux through the surface of the box were zero, could you conclude that there were no charges inside the box? Why or Why not?
Solution
- Φ = 8 × 103 N m2 C-1
or `q/ε_0 = 8 xx 10^3` N m2 C-1
or q = 8 × 103ε0
= 8 × 103 × 8.85 × 10-12
or q = 7.08 × 10-8 C - As Φ = 0
or `q_"net"/ε_0 = 0 or q_"net" = 0`
Even though a closed surface may have internal charges, the net charge it contains is zero.
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