- #1
JeeebeZ
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Homework Statement
The power supply for a stereo amp develops an output of 22 volts at 2.8 amps. If the overall efficiency of the power supply is 78%, what is the input current that it will draw from a 117 volt source.
Homework Equations
P = EI
The Attempt at a Solution
Eo = 22 V
Io = 2.8 Amps
Po = 22 * 2.8 = 61.6 watts
Pi = 61.6 / .78 (efficiency) = 79.0 watts
Ei = 117 V
Ii = 117 / 79.0 = 1.48 ampsBasically is this right?
I thought what you put in always has to be bigger then what you get out?
if so then how can 1.48 amps in = 2.8 amps out?