Problem 10: An MP3 player has a charger that can be plugged into the wall power

Question

Problem 10: An MP3 player has a charger that can be plugged into the wall power outlet at 120 V AC and converts to 5 V AC as indicated on the transformer label. The maximum instantaneous current from the power outlet that the transformer can handle is 140 mA. (a) What is the average power that the transformer can handle? (b) What is the maximum instantaneous current on the output (player) side that the transformer can deliver? (c) If you choose 1200 turns on your input coil, how many turns should the output coil have? Concept: Solution:

Explanation / Answer

Here ,

Vp = 120 V

Vs = 5 V

Ip = 140 mA = 0.140 A

a) average power transferred = Vp * Ip

average power transferred = 120 * 0.140

average power transferred = 16.8 W

b)

for the output current

Ip * 5 = 0.140 * 120

Ip = 3.36 A

the maximum current is 3.36 A

c)

let the number of output coils is Ns

Ns/Np = Vs/Vp

Ns/1200 = 5/120

NS = 50

the number of output coils is 50

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