Question

Two short bar magnets of same magnetic moment each of $0.25A{m}^2$ are arranged in parallel and aligned with each other 1 metre apart. The induction field strength at the centre of the common equatorial line joining the two centres of the magnets is:

• A. ${10}^{-7}$ T
• B. $2\times {10}^{-7}T$
• C. $zero$
• D. $4\times {10}^{-7}T$

Answer 1

The correct option is B $2\times {10}^{-7}T$

$m_1=m_2=0.25A{m}^2$
$B_1=B_2=\frac{{\mu }_{0}m}{4\pi d^2}$
$d=0.5m$

Since magnets are arranged in parallel and are aligned in the same direction, fields due to the magnets add up.
$B=B_1+B_2$
$=\frac{2\times {\mu }_{0}m}{4\pi d^2}$
$=\frac{2\times {10}^{-7}\times 0.25}{{0.5}^2}$
$=2\times {10}^{-7}T$