A transformer for a laptop computer converts a 120-V input to a 24-V output. If the output current for the transformer is 1.8 A, find the input current.

To find for the input current, we use ratio and proportion concept. We use the equation:

I (input) / I (output) = V (output) / V (input)

I (input) / 1.8 A = 24 V / 120 V

I (input) = 0.36 A

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