Let the two coil P and Q having same length and number of turns NP=4 and NQ=2 Then, l=NP2πRP=NQ2πRQ where, RP= radius of coil P. and RQ= radius of coil Q. Now, ‌
RP
RQ
=‌
NQ
NP
=‌
2
4
=‌
1
2
. . . (i) If same current is passing through P and Q. Then, ‌