Q. Two concentric circuit coils of ten turn each are situated in the same plane. Their radii are 20 cm and 40 cm and they carry respectively 0.2 A and 0.3 A current in opposite direction. The magnetic field in tesla at the centre is
A) $35\ \mu_{0}/4$ T
B) $\mu_{0}/80$ T
C) 7 $\mu_{0}/80$ T
D) 5 $\mu_{0}/4$ T
Explanation
(d) $B = \ \frac{\mu_{0}ni_{1}}{2r_{1}} - \frac{\mu_{0}ni_{2}}{2r_{2}}$
$= \ \mu_{0}\left\lbrack \frac{10 \times 0.20}{2 \times 0.20} - \frac{10 \times 0.30}{2 \times 0.40} \right\rbrack = \frac{5}{4}\mu_{0}.$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.