Red Seal Electrician Practice
TransformersQuestion 1428 of 1506

A single-phase transformer steps 480 V down to 120 V. The secondary load current is 100 A. What is the primary current?

  1. 43.3 A
  2. 25.0 A
  3. 75.0 A
  4. 100 A
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Correct answer: 25.0 A

Ip = Is × (Vs ÷ Vp) = 100 × (120 ÷ 480) = 25.0 A. The higher voltage side carries the lower current.

Source: Computed, 1.1: What is Alternating Current (AC)?

Practice transformers

Questions last reviewed: 18 October 2026