A stereo system draws 2.4 A at 120 V. The audio output power is 50 W.
a- How much power is lost in the form of heat in the system?
b- What is the efficiency of the system?
if the output power is 50W, the efficiency of the output is
50W/288W ~ 17%
how much power is lost to heat is not obvious. there are other sources of losses besides heat (the efficiency of the speakers themselves etc etc).
but i guess we're supposed to assume that all inefficiency goes into heat. if so, 288W-50W = 238W is lost to heat (?).
If the 120V input is peak voltage of an alternating current... and if the waveform is a sine wave you'll have to multiply by the average value of a sine wave which is the squareroot of 2 divided by 2... approximately 0.707 * peak...
That means that the average voltage is 84.84 volts, multiplying that by 2.4amps = 203.616 watts
153.616 watts of power are lost due to inefficiencies.
If the stereo system is 50 watts per channel; and using ohms law, the output would equal around .8 amps: which means that 1.6 amps of power is unaccounted for...due to heat, or resistance, or a small amount of voltage drop. Not sure about the effiecency...but it would not seem to be all that great.
if the output power is 50W, the efficiency of the output is
50W/288W ~ 17%
how much power is lost to heat is not obvious. there are other sources of losses besides heat (the efficiency of the speakers themselves etc etc).
but i guess we're supposed to assume that all inefficiency goes into heat. if so, 288W-50W = 238W is lost to heat (?).