Bài 3.
a)\(R_1ntR_2\Rightarrow R_{tđ}=R_1+R_2=2+4=6\Omega\)
b)\(U=I\cdot R_{TĐ}=0,5\cdot6=3V\)
c)\(R_3//\left(R_1ntR_2\right)\Rightarrow R_{TĐ}=\dfrac{R_{12}\cdot R_3}{R_{12}+R_3}=\dfrac{6\cdot3}{6+3}=2\Omega\)
\(I_{mạch}=\dfrac{U}{R_{tđ}}=\dfrac{3}{2}=1,5A\)
Bài 4.
a)\(R_1//R_2\Rightarrow R_{12}=\dfrac{R_1\cdot R_2}{R_1+R_2}=\dfrac{4\cdot6}{4+6}=2,4\Omega\)
b)\(U=I\cdot R=I_A\cdot R_{TĐ}=0,5\cdot2,4=1,2V\)
c)\(R_3nt\left(R_1//R_2\right)\Rightarrow R_{tđ}=R_3+R_{12}=1,6+2,4=4\Omega\)
\(I=\dfrac{U}{R}=\dfrac{1,2}{4}=0,3A\)
Đúng 3
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