Chapter 21 - AC Circuits - Learning Path Questions and Exercises - Exercises - Page 749: 22

a) $0.239H$ b) $120Hz$

a) $X_{L}=90 Ohm$ $f=60Hz$ $X_{L}=2\times pi \times f\times L$ Thus, $L=\frac{90}{2\times3.14\times60}=0.239H$ b) As $X_{L}$ is directly proportional to f, to double the reactance, we have to double the frequency as well. i.e. $120Hz$