Đáp án:
\(\begin{array}{l}
a.\\
B = 3,{333.10^{ - 6}}\\
b.\\
B = {8.10^{ - 6}}
\end{array}\)
Giải thích các bước giải:
\(\begin{array}{l}
a.\\
B = |{B_1} - {B_2}| = |{2.10^{ - 7}}.\frac{{{I_1}}}{{{r_1}}} - {2.10^{ - 7}}.\frac{{{I_2}}}{{{r_2}}}| = |{2.10^{ - 7}}.\frac{2}{{0,04}} - {2.10^{ - 7}}.\frac{4}{{0,06}}| = 3,{333.10^{ - 6}}\\
b.\\
B = {B_1} + {B_2} = {2.10^{ - 7}}.\frac{{{I_1}}}{{{r_1}}} + {2.10^{ - 7}}.\frac{{{I_2}}}{{{r_2}}} = {2.10^{ - 7}}.\frac{2}{{0,1}} + {2.10^{ - 7}}.\frac{4}{{0,2}} = {8.10^{ - 6}}
\end{array}\)