Bài 4
R1//R2\(=>RTd=\dfrac{R1R2}{R1+R2}=\dfrac{18.12}{18+12}=7,2\left(ôm\right)\)
b,\(=>Uv=U1=U2=Um=36V=>Ia=\dfrac{Um}{Rtd}=\dfrac{36}{7,2}=5A\)\(=>Ia1=\dfrac{U1}{R1}=\dfrac{36}{18}=2A=>Ia2=Ia-Ia1=3A\)
bài 5
R1//R2//R3 \(=>\dfrac{1}{Rtd}=\dfrac{1}{R1}+\dfrac{1}{R2}+\dfrac{1}{R3}=>Rtd=6\left(ôm\right)\)
b,\(=>U1=U2=U3=U=45V=>Im=\dfrac{U}{Rtd}=\dfrac{45}{6}=7,5A\)\(=>I1=\dfrac{U1}{R1}=\dfrac{45}{15}=3A=>I2=\dfrac{U2}{R2}=\dfrac{45}{20}=2,25A\)
\(=>I3=\dfrac{U3}{R3}=2,25A\)
bài 6
R1//R2
a,\(=>Um=Ia1.R1=0,5.15=7,5V\)
b,\(=>Ia=\dfrac{Um}{\dfrac{R1R2}{R1+R2}}=\dfrac{7,5}{\dfrac{15.10}{15+10}}=1,25A\)
