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06/05/2021 3:12 pm

A soldering iron uses an electric current in a wire to heat the tip. A transformer with 100 turns on the secondary coil provides 51 W at an rms voltage of 28 V. Assume that the soldering iron is plugged into a 120 V outlet. What is the resistance of the wire in the iron? How many turns are in the primary coil? What is the current in the primary coil?

06/05/2021 3:13 pm

"What is the resistance of the wire in the iron?"

P = V^2/R. You have P and V.

"How many turns are in the primary coil?"

Ratio of turns = ratio of voltages = 120:28

That is, x/100 = 120/28

"What is the current in the primary coil?"

P = I * V and you have P and V.