Red Seal Electrician Practice
AC theoryQuestion 481 of 1506

Two quantities act at 90 degrees to each other, such as resistance and reactance. How must they be added?

  1. Arithmetically, by plain addition
  2. By subtracting the smaller from the larger
  3. Vectorially, using the Pythagorean theorem
  4. By multiplying them
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Correct answer: Vectorially, using the Pythagorean theorem

Quantities at right angles cannot be added normally.

Source: Trigonometry and Single Phase AC Generation for Electricians (Flinn), 1.2: Triangles

Practice ac theory

Questions last reviewed: 18 October 2026