9.\(F=k\cdot\dfrac{\left|q_1q_2\right|}{\varepsilon\cdot r^2}\)
\(\Rightarrow B\)
10.\(A_{ng}=\xi\cdot I\cdot t\)\(\Rightarrow C\)
11.\(\Rightarrow A\)
13.\(\Rightarrow D\)
14.\(C=\dfrac{Q}{U}\Rightarrow A\)
15.\(\Rightarrow D\)
16.\(U=\dfrac{A}{q}=\dfrac{-6}{-2}=3V\Rightarrow D\)
17.\(F=k\cdot\dfrac{\left|q_1q_2\right|}{r^2}=9\cdot10^9\cdot\dfrac{\left|10^{-7}\cdot4\cdot10^{-7}\right|}{r^2}=0,1\)
\(\Rightarrow r=0,06m=6cm\Rightarrow B\)
18.\(F=k\cdot\dfrac{\left|q_1q_2\right|}{r^2}=9\cdot10^9\cdot\dfrac{\left|-4\cdot10^{-5}\cdot5\cdot10^{-5}\right|}{0,05^2}=7200N\Rightarrow B\)