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If the secondary coil is attached to a load that allows current to flow, electrical power is transmitted from the primary circuit to the secondary circuit.Ideally,the transformer is perfectly efficient; all the incoming energy is transformed from the primary circuit to the magnetic field and into the secondary circuit. If this condition is met, the incoming electric power must equal the outgoing power.
Pincoming = IPVP = Poutgoing = ISVS
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giving the ideal transformer equation
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If the voltage is increased, then the current is decreased by the same factor.