Ta có:
\(\left\{ \matrix{ {B_1} = 4\pi {.10^{ - 7}}{{{N_1}} \over {{l_1}}}{I_1} \hfill \cr {B_2} = 4\pi {.10^{ - 7}}{{{N_2}} \over {{l_2}}}{I_2} \hfill \cr} \right.\)
Ta thấy:
\(\left\{ \matrix{ {{{N_1}} \over {{l_1}}}{I_1} = {{5000.5} \over 2} = 12500 \hfill \cr {{{N_2}} \over {{l_2}}}{I_2} = {{10000.2} \over {1,5}} = {{40000} \over 3} \approx 13333,3 \hfill \cr} \right. \)
\(\Rightarrow {{{N_1}} \over {{l_1}}}{I_1} < {{{N_2}} \over {{l_2}}}{I_2} \Rightarrow {B_1} < {B_2}\)
