Biết độ lớn cảm ứng từ do một dây dẫn thẳng dài mang dòng điện I tạo ra ờ vị trí cách trục dây dẫn một khoảng r là \(B = 2,{0.10^{ - 7}}\left( {\frac{I}{r}} \right),\) với B tính bằng tesla \(({\rm{T}}),r\) tính bằng mét (m) và I tính bằng ampe (A). Một dây dẫn thẳng dài 2 m mang dòng điện 10 ampe. Độ lớn cảm ứng từ do dòng điện gây ra ở vị trí cách nó 2 cm lớn gấp mấy lần so với ở khoảng cách 4 cm?
Biết độ lớn cảm ứng từ do một dây dẫn thẳng dài mang dòng điện I tạo ra ờ vị trí cách trục dây dẫn một khoảng r là \(B = 2,{0.10^{ - 7}}\left( {\frac{I}{r}} \right),\) với B tính bằng tesla \(({\rm{T}}),r\) tính bằng mét (m) và I tính bằng ampe (A). Một dây dẫn thẳng dài 2 m mang dòng điện 10 ampe. Độ lớn cảm ứng từ do dòng điện gây ra ở vị trí cách nó 2 cm lớn gấp mấy lần so với ở khoảng cách 4 cm?
Hãy suy nghĩ và trả lời câu hỏi trước khi xem đáp án
Ta có:
$B_1 = 2 \cdot 10^{-7} \cdot \frac{I}{r_1} = 2 \cdot 10^{-7} \cdot \frac{10}{0.02}$
$B_2 = 2 \cdot 10^{-7} \cdot \frac{I}{r_2} = 2 \cdot 10^{-7} \cdot \frac{10}{0.04}$
Khi đó: $\frac{B_1}{B_2} = \frac{0.04}{0.02} = 2$.
Vậy độ lớn cảm ứng từ tại vị trí cách dây 2cm lớn gấp 2 lần so với độ lớn cảm ứng từ tại vị trí cách dây 4cm.
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