Question

A small transformer to recharge the battery in a cell phone is plugged into a wall...

A small transformer to recharge the battery in a cell phone is plugged into a wall socket that has 120 volts RMS and a maximum available current of 20 Amps. The secondary coil of the transformer has 14 turns, and the output voltage of the transformer is 5.5V (DC). The recharger takes 440mA out from the transformer. Assume the transformer is ‘ideal’, with and efficiency of 100 percent.

  1. What is the resistance of the battery recharger from the cell phone?

  1. How many turns are on the primary coil of the transformer?

  1. How much power is coming out from the transformer, into the recharger?

  1. How much current from the wall socket is in the primary coil of the transformer?

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