Finding inductance and maximum energy for 240V 50Hz inductor with 4A current

[jendrix]

Homework Statement

Assuming steady-state sinusoidal ac.A voltage of 240V at 50Hz applied to an inductor yields a current of 4A.Assume negligible resistance.Find inductance, max stored energy.

Homework Equations

E=0.5Li^2

X=2*pi*f*L

The Attempt at a Solution

V/I=X Which I found to be 60

L=60/2*pi*f
L=0.191H

E=0.5*0.191*4^2
E=1.528J

However the answer given is 3.06J , which has left me confused.

Thanks

 

[gneill]

The given voltage and current values are no doubt RMS values...

 

[PhysicoRaj]

assuming steady-state sinusoidal ac.a voltage of 240v at 50hz applied to an inductor yields a current of 4A. Assume negligible resistance. Find inductance, max stored energy.

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Maximum energy is stored when maximum current flows through it.

 

[jendrix]

Of course, I need to use I pk,

so E=0.5*0.191*(4*2^1/2)^2=3.06J

Thanks :)