Answer to Question #162931 in Field Theory for Miracle Nwabueze

Question

A rectangular 40-loop coil, 10cm x 12cm, carrying a current of 2A is in the vicinity of an external magnetic field. This external magnetic field has the same magnitude as that set up at the centre of an 800-loop circular coil (32cm in diameter) carrying a current of 80A. What will be the maximum torque experienced by the rectangular coil?

Answer 1

Answer

Magnetic field due to circular coil

$B=\frac{N\mu_0i}{2R}\\=\frac{800\times12.57\times10^{-7}\times80}{0.16}\\=0.51T$

Magnetic moment

$M=NiA\\=40\times2\times0.1\times0.12$

=0.96Am²

So torque

$\tau=MB\\=0.96\times0.51\\=0.49Am^2T$