Net magnetic field due to loop ABCD at O is B=BAB+BBC+BCD+BDA=0+4πaμoI×6π+0−4πbμoI×6π=24aμoI−24bμoI=24abμoI(b−a) 
JEE Main 2009 — Physics Electromagnetism
The magnitude of the magnetic field (B) due to loop ABCD at the origin (O) is
Held on 30 Apr 2009 · Verified 6 Jul 2026.
zero
24abμ0(b−a)
4πμ0I[abb−a]
4πμo∣[2(b−a)+3π(a+b)]
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