**A step-up transformer has a turns ratio of 840 and is operating to produce a secondary voltage of 90 kV in order to power a device with 9 kilowatts. If the transformer is 90% efficient, what is the current in the primary winding of the transformer?**

**Answer:**

90% efficient means 10 kw input … current = 10 kw / (90 kv / 840)