# Physics - Help!!!

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I am having trouble understanding transformers!!
Here is the problem I have to solve:
A protable CD player requires 12 volts to operate. A transformer allows the device to be powered from a 120-volt outlet. If the primary has 500 turns, how many turns should the secondary have?
This is how I set it up:
(primary voltage)/(number of primary turns) = (secondary voltage)/(number of secondary turns)
12/500 = 120/5000
but I have no idea if I am on the right track!

• Physics - Help!!! -

U1/U2 =N1/N2
N2 =N1•U2/U1 =500•12/120 = 50

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