Uma carga pontual produz um fluxo elétrico de -750 Nm²/C

-0,75

\[\eqalign{ & \Phi = EA \cr & \Phi = 4\pi {r^2}\left( {\dfrac{{kQ}}{{{R^2}}}} \right) \cr & - 750 = 4\pi {\left( {0,1} \right)^2}\left( {\dfrac{{9 \cdot {{10}^9} \cdot C}}{{{{\left( {0,2} \right)}^2}}}} \right) \cr & - 750 = 0,125\left( {2,25 \cdot {{10}^{11}}C} \right) \cr & - 750 = 2,8 \cdot \,{10^{10}}C \cr & C = - 2,6 \cdot {10^{ - 8}}{\text{ C}} }\]

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Portanto, \(\boxed{C = - 2,6 \cdot {{10}^{ - 8}}{\text{ C}}}\).

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Já o novo fluxo será:

\[\eqalign{ & \Phi = 4\pi kq \cr & \Phi = 4\pi {r^2}\left( {\dfrac{{kQ}}{{{R^2}}}} \right) \cr & \Phi = = 4\pi \left( {9 \cdot {{10}^9}} \right)\left( {2,8 \cdot \,{{10}^{10}}} \right) \cr & \Phi = 31,6 \cdot {10^{20}}{\text{ N}}{{\text{m}}^2}{\text{/C}} }\]

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Portanto temos que \(\boxed{\Phi = 31,6 \cdot {{10}^{20}}{\text{ N}}{{\text{m}}^2}{\text{/C}}}\).