If in circular coil of radius `R`, current `I` is flowing and in another coil `B` of radius `2R` a current `2I` is flowing , then the raatio of the magnetic fields `B_(A) and B_(B)`, produced by them will be

Options

A. 1
B. 2
C. `1//2`
D. 4

Answer

A

Explanation

Magnetic field in circular coil A is `B_(A)=(mu_(0)NI)/(2R)` where R is radiusand I is current flowing in coil.
Similarly `B_(B)=(mu_(0)N(2I))/(2.(2R))=(mu_(0)NI)/(2R):. (B_(A))/(B_(B))=1`