Two inductances connected in parallel are equivalent to a single inductance of `1.5H` and when connected in series are equivalent to a single inductance of 0.8 H. The difference in their inductance is

Options

A. 3 H
B. 7.5 H
C. 2 H
D. 4 H

Answer

D

Explanation

`therefore` In parallel, `L_(P)=(L_(1)L_(2))/(L_(1)+L_(2))`
`(L_(1)+L_(2))1.5=L_(1)L_(2)`
and in series, `L_(s)=L_(1)+L_(2)=8`
`therefore" "L_(1)L_(2)=12`
`(L_(1)-L_(2))^(2)=(L_(1)+L_(2))^(2)-4L_(1)L_(2)`
`L_(D)=sqrt((8)^(2)-4xx12)`
`L_(D)=4 H`