Answer :
Given
The input voltage, V=120 V
The output voltage, V'=12.0 V
Current output is I'=355 mA
To find
(b) What is the power input (in W)?
Explanation
We know,
[tex]\begin{gathered} VI=V^{\prime}I^{\prime} \\ \Rightarrow120I=12\times355\times10^{-3} \\ \Rightarrow I=0.0355\text{ A} \end{gathered}[/tex]The power input is
[tex]\begin{gathered} P=IV \\ \Rightarrow P=120\times0.0355 \\ \Rightarrow P=4.26\text{ W} \end{gathered}[/tex]Conclusion
The power input is 4.26 W