A portable x-ray unit has a step-up transformer. The 120 V input is transformed to the 100 kV output needed by the x-ray tube. The primary has 47 loops and draws a current of 16 A when in use. What is the current output of the secondary in milliAmpere

Question

Physics

Rayna Dyer

9 May, 06:15

A portable x-ray unit has a step-up transformer. The 120 V input is transformed to the 100 kV output needed by the x-ray tube. The primary has 47 loops and draws a current of 16 A when in use. What is the current output of the secondary in milliAmpere

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Davon Mahoney · Answer 1

The number of loops in the primary winding of the transformer draws our attention to it like some kind of consciousness-magnet. But if and when we start to actually THINK about this question, we notice a subtle bad smell, and we realize that the number of loops in the transformer is a total red herring, and we don't need to worry about it at all.

- - The electrical power coming out of the transformer is equal to the electrical power going into it.

- - Electrical power = (voltage) x (current)

- - Power going in = (120 V) x (16 A) = 1,920 watts

- - Power coming out = (100,000 V) x (current)

100,000v x current = 1,920 W

Current = 1,920 W / 100,000 V

Current = 0.0192 A

Current = 19.2 milliAmperes

Leave the red herring where we found it and let it rot.