Two current carying circular coils A and B, having the same number of turns are connected in series. What is the ratio of the magnetic inductions produced at their centres, in the diameters of A and B are 10 cm and 20 cm respectively ?

Options

A. `1/2`
B. `1/3`
C. `2:1`
D. `3:1`

Answer

C

Explanation

Thet coils are connected in series. Hence the same current flows through them or `I_(1) =I_(2) and n_(1)=n_(2)`
`B =(mu_(0))/(4pi) ((2pi nI)/(r))`
In this case, `[(mu_(0))/(4pi)xx2pinI]` is constant.
`therefore B prop 1/r therefore (B_(1))/(B_(2))=(r_(2))/(r_(1))=10/5 =2:1`