theo bài ra \(=>R1ntR2ntR3ntR4\)

\(=>Rtd=R1+R2+R3+R4\)

\(=R1+\dfrac{R1}{2}+\dfrac{R1}{3}+\dfrac{R1}{4}=\dfrac{24R1+12R1+8R1+6R1}{24}\)

\(=\dfrac{50R1}{24}\left(om\right)\)

\(=>Im=\dfrac{50}{Rtd}=\dfrac{50}{\dfrac{50R1}{24}}=\dfrac{24}{R1}A=I1=I2=I3=I4\)

\(=>U1=I1.R1=\dfrac{24}{R1}.R1=24V\)

\(=>U2=I2.R2=\dfrac{24}{R1}.\dfrac{R1}{2}=12V\)

\(=>U3=I3.R3=\dfrac{24}{R1}.\dfrac{R1}{3}=8V\)

\(=>U4=I4.R4=\dfrac{24}{R1}.\dfrac{R1}{4}=6V\)

\(=>Im=I1=I2=I3=I4=\dfrac{U}{RTd}=\dfrac{100}{R1+\dfrac{R1}{2}+\dfrac{R1}{3}+\dfrac{R1}{4}}\)

\(=\dfrac{100}{\dfrac{24R1+12R1+8R1+6R1}{24}}=\dfrac{2400}{50R1}\left(A\right)\)

\(=>U1=I1.R1=\dfrac{2400}{50}=48V\)

\(=>U2=I2.R2=\dfrac{2400}{50R1}.\dfrac{R1}{2}=24V\)

\(=>U3=I3.R3=\dfrac{2400}{50.3}=16V\)

\(=>U4=I4.R4=\dfrac{2400}{50.4}=12V\)

không có hình vẽ mà tui thấy bài 4: đoạn mạnh nối tiếp nên chắc 5 điện trở nối tiếp chăng?

R1 nt R2 nt R3 nt R4 nt R5

\(=>Im=I1=I2=I3=I4=I5=\dfrac{U}{R1+R2+R3+R4+R5}\)

\(=\dfrac{5}{R1+\dfrac{R1}{2}+\dfrac{R1}{3}+\dfrac{R1}{4}+\dfrac{R1}{5}}=\dfrac{5}{\dfrac{120R1+60R1+40R1+30R1+24R1}{120}}\)

\(=\dfrac{5}{\dfrac{274R1}{120}}=\dfrac{600}{274R1}=\dfrac{300}{137R1}A\)

\(=>U1=I1.R1=\dfrac{300}{137}V\)

\(=>U2=I2R2=\dfrac{300}{137.2}=\dfrac{150}{137}V\)

\(=>U3=\dfrac{300}{137.3}=\dfrac{100}{137}V\)

\(=>U4=\dfrac{300}{137.4}=\dfrac{75}{137}V\)

\(=>U5=\dfrac{300}{137.5}=\dfrac{60}{137}V\)

Bài 1.

\(R_{tđ}=\dfrac{U}{I}=\dfrac{75}{2,5}=30\Omega\)

Có \(R_1ntR_2\Rightarrow R_1+R_2=30\) \(\Rightarrow2R_2+R_2=30\Rightarrow R_2=10\Omega\)

\(\Rightarrow R_1=30-R_2=30-10=20\Omega\)

BÀI 2.

Ta có:  \(R_{tđ}=\dfrac{U}{I}=\dfrac{45}{2,5}=18\Omega\)

Mà \(R_1//R_2\) \(\Rightarrow\dfrac{1}{R}=\dfrac{1}{R_1}+\dfrac{1}{R_2}\)

Lại có:  \(R_1=\dfrac{3}{2}R_2\)

\(\Rightarrow\dfrac{1}{R}=\dfrac{1}{\dfrac{3}{2}R_2}+\dfrac{1}{R_2}=\dfrac{1}{18}\) \(\Rightarrow R_2=30\Omega\)

\(I=I1=I2=I3=U3:R3=7,5:5=1,5A\left(R1ntR2ntR3\right)\)

\(\Rightarrow\left\{{}\begin{matrix}U1=I1\cdot R1=1,5\cdot4=6V\\U2=I2\cdot R2=1,5\cdot3=4,5V\\U=U1+U2+U3=6+4,5+7,5=18V\end{matrix}\right.\)

\(R_{tđ}=R_1+R_2+R_3=4+3+5=12\Omega\)

\(U_3=7,5V\Rightarrow I_3=1,5A\)

\(\Rightarrow I_m=I_1=I_2=I_3=1,5A\)

\(\Rightarrow U_1=1,5\cdot4=6V\)

     \(U_2=1,5\cdot3=4,5V\)

     \(U_m=U_1+U_2+U_3=6+4,5+7,5=18V\)

Bạn tự làm tóm tắt nhé!

Điện trở tương đương: \(R=\dfrac{U}{I}=\dfrac{50}{1}=50\Omega\)

Điện trở R₃: \(R=R_1+R_2+R_3\Rightarrow R_3=R-\left(R_1+R_2\right)=50-\left(5+20\right)=25\Omega\)

\(I=I_1=I_2=I_3=1A\left(R_1ntR_2ntR_3\right)\)

Hiệu điện thế giữa hai đầu mỗi điện trở:

\(U_1=R_1.I_1=5.1=5V\)

\(U_2=R_2.I_2=20.1=20V\)

\(U_3=R_3.I_3=25.1=25V\)