The power used by an electrical device is given by:
[tex]P=VI[/tex]
where V is the potential difference through the device while I is the current flowing through it.
For the cd-player in our problem, [tex]V=3.0 V[/tex], while the current is
[tex]I=330 mA=0.33 A[/tex]
Therefore, the power used is
[tex]P=VI=(3.0 V)(0.33 A)=0.99 W[/tex]
