a) Ta có: \(R_1\) nối tiếp \(R_2\)
\(\Rightarrow R_{tđ}=R_1+R_2\)
\(\Rightarrow R_{tđ}=15+10\)
\(\Rightarrow R_{tđ}=25\Omega\)
b) Ta có: \(I=\dfrac{U}{R}\)
\(\Rightarrow I=\dfrac{12}{25}=0,48\left(A\right)\)
mà \(R_1\) nối tiếp \(R_2\)
\(\Rightarrow I=I_1=I_2\left(=0,48A\right)\)