Worksheet: Transformation of Current and Voltage

In this worksheet, we will practice calculating the current and voltage changes due to electromagnetic induction using a step-up or step-down transformer.


A 100% efficient transformer is used to step down 110 V from a wall socket to 9.0 V for a radio.

If the primary winding has 500 turns, how many turns does the secondary winding have?

If the radio operates at a current of 500 mA, what is the current through the primary winding?


A step-up transformer connected to a 110 V line is used to supply a hydrogen gas discharge tube with 5.0 kV (rms). The tube dissipates 75 W of power.

What is the ratio of the number of turns in the secondary winding to the number of turns in the primary winding?

  • A 3 0 1
  • B 4 0 1
  • C 5 5 1
  • D 2 5 1
  • E 4 5 1

What is the rms current in the primary winding?

What is the rms current in the secondary winding?

What is the effective resistance seen by the 110 V source?

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