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Module 3. Electrical fundamentals

In a 4:1 step-up transformer, 120V is applied to the primary, and the load on the secondary is 1600 Ohms. What is the current in the primary?

  • 0.075A
  • 1.2A
  • 3A

Explanation

The 4:1 step-up turns 120 V into 480 V across the 1600-ohm load, giving a secondary current of 480/1600 = 0.3 A and a load power of 144 W. With negligible losses the primary draws the same power, so primary current is 144 W / 120 V = 1.2 A, which is also four times the 0.3 A secondary current.

marinos_98 asking:

Can anyone explain that?

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