Question

what is the magnitude of the equatorial field due to a bar magnet of length is 8 cm and distance 0.5 m from its midpoint ?{ magnetic moment i= 0.4 Am square}​

Answer 1

Magnitude of the equatorial field due to bar magnet is :

• Given : length, 2l = 8 cm = 8×10^-2 m

Perpendicular distance from its midpoint, r= 0.5 m

Magnetic moment, M = 0.4 Am^2

• We know that, magnetic field at equatorial positiom is given as

$B = μo×M / 4\pi( r^2 + l^2 )^{3 / 2} \:$

• μo/4π = 10^-7 H/m

• Substituting values in formula,

• B = 10^-7 × 0.4 / [ (0.5)^2 + (8×10^-2)^2 ]^3/2

In (0.5)^2 + (8×10^-2)^2 , (8×10^-2)^2 <<< 1

• Therefore, we can neglect that term from calculations

B = 0.4×10^-7 /[ (0.5)^2 ]^3/2

= 0.4×10^-7 / (0.5)^3

= 3.2×10^-7 T