Let r1 and r2 be the radius of coil 1 and coil 2 . If B1 and B2 are magnetic induction at their centre then B1=2r1μ0I1 and B2=2r2μ0I2 B1=B2 and r1=2r2 there I1=2I2 Again if R1 and R2 are resistance of the coil 2 then R1=2R2 (as R∝ length =2πr) and if v1 and v2 are the potential difference across them respectively then V2V1=I2R2I1R1=I2R2(2I2)(2R2)=4