A coil of `Cu` wire (radius `r`, self-inductance `L`) is bent in two concentric turns each having radius `(r )/(2)`. The self-inductance now

Options

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

Answer

A

Explanation

` therefore LpropN^(2)r,`" "`(L_(1))/(L_(2))=(N_(1)/(N_(2)))^(2)xx(r_(1))/(r_(2))`
`implies(L)/(L_(2))=((1)/(2))^(2)xx((r)/(r//2))=(1)/(2), L_(2)=2L`