Chương I- Điện tích. Điện trường

Sự nở vì nhiệt nếu bị ngăn cản thì sẽ gây dần lớn gì

a/ \(F=\dfrac{k\left|q_1q_2\right|}{r^2}=\dfrac{9.10^9.5.10^{-7}.8.10^{-7}}{0,2^2}=...\left(N\right)\)

b/ \(\left|q_1\right|< \left|q_2\right|\Rightarrow\) C gần q1 hơn

\(\Rightarrow\dfrac{k\left|q_1\right|}{AC^2}=\dfrac{k\left|q_2\right|}{\left(AB+AC\right)^2}\Leftrightarrow\dfrac{5}{AC^2}=\dfrac{8}{\left(0,2+AC\right)^2}\Rightarrow AC=...\left(m\right)\)

Vẽ hình thì khỏi đi, xem trong SGK ý

\(F=\dfrac{k\left|q_1q_2\right|}{r^2}=\dfrac{9.10^9.4.10^{-6}.8.10^{-6}}{0,1^2}=...\left(N\right)\)

b/ \(E_1=\dfrac{k\left|q_1\right|}{\left(\dfrac{1}{2}r\right)^2};E_2=\dfrac{k\left|q_2\right|}{\left(\dfrac{1}{2}r\right)^2}\)

\(\overrightarrow{E_1}\uparrow\uparrow\overrightarrow{E_2}\Rightarrow\sum E=E_1+E_2=...\left(V/m\right)\)

c/\(\left|q_1\right|>\left|q_2\right|\Rightarrow\) gần q2 hơn

 \(E_1=E_2\Leftrightarrow\dfrac{k\left|q_1\right|}{\left(AB+r'\right)^2}=\dfrac{k\left|q_2\right|}{r'^2}\Leftrightarrow\dfrac{4}{\left(0,1+r'\right)^2}=\dfrac{8}{r'^2}\Rightarrow r'=....\left(m\right)\)

\(m=\dfrac{A.I.t}{F.n}=\dfrac{64.1.10.60}{96500.2}=...\left(kg\right)\)

\(m=S.h\Rightarrow h=\dfrac{m}{S}=...\left(cm\right)\)

\(\overrightarrow{A_{AC}}=q.\overrightarrow{E_{AC}}.\overrightarrow{AC}\Rightarrow A_{AC}=-1,6.10^{-19}.3000.0,08=...\left(J\right)\)

\(\overrightarrow{A_{BC}}=q.\overrightarrow{E_{BC}}.\overrightarrow{BC}=-1,6.10^{-19}.3000.0,06.\cos90^0=...\left(J\right)\)

\(R_D=\dfrac{U^2_{dm}}{P_{dm}}=6\left(\Omega\right)\Rightarrow I=I_D=\dfrac{\xi}{r+R+R_D}=\dfrac{18}{1+2+6}=2\left(A\right)\)

\(\cot\alpha=\dfrac{P}{F};\sin\alpha=\dfrac{r}{2l};1+\cot^2\alpha=\dfrac{1}{\sin^2\alpha}\)

\(\cot\alpha=\dfrac{mg}{\dfrac{kq^2}{r^2}}=\dfrac{mgr^2}{kq^2}=...\)

\(\Rightarrow\sin\alpha=...\Rightarrow l=...\left(m\right)\)

\(E_A=\dfrac{kq}{r_A^2}=36;E_B=\dfrac{kq}{\left(r_A+AB\right)^2}=9\)

\(\Rightarrow\dfrac{E_A}{E_B}=\dfrac{\left(r_A+AB\right)^2}{r^2_A}=4\Leftrightarrow r_A+AB=2r_A\Leftrightarrow r_A=AB\)

\(E_M=\dfrac{kq}{\left(r_A+\dfrac{AB}{3}\right)^2}=\dfrac{kq}{\left(\dfrac{4}{3}r_A\right)^2}=\dfrac{9}{16}.E_A=...\left(V/m\right)\)