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Three resistors in parallel have an equivalent resistance of 3 ohms. If two of resistors have values 10 and 5 ohms, what is the resistance of the third resistor | Basic Electrical Engineering MCQ#7

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Three resistors in parallel have an equivalent resistance of 3 ohms. If two of resistors have values 10 and 5 ohms, what is the resistance of the third resistor:

  1. 15 ohms
  2. 25 ohms
  3. 30 ohms
  4. 50 ohms

Correct answer: 30 ohms

MCQ Answer Explanation

(1/R1) + (1/R2) + (1/R3) = (1/Req)

(1/10) + (1/5) + (1/R3) = (1/3)

(1/R3) = (1/3) – (1/10) – (1/5)

1/R3 = 0.33333 – 0.1 – 0.2

1/R3 = 0.03333

R3 = 30 ohms

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