NICET Level I Fire Alarm Systems Pop Quiz #3

When 2 resistors are connected together their total resistance is calculated at 500 Ohms. What is the resistance value of each resistor?

a. R1 = 100 Ohms / R2 = 300 Ohms

b. R1 = 1,000 Ohms /  R2 = 1,000 Ohms

c. R1 = 500 Ohms / R2 = 500 Ohms

d. R1 = 500 Ohms / R2 = 250 Ohms

Answer in comments.

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One Comment

  1. Answer:

    This question you just have to connect the resistors in series and parallel and check their total resistance for:
    Series => When resistors are in series they add to combine. If we calculate the total resistance for each of the multiple choices above we get…
    a. 100 Ohms + 300 Ohms = 400 Ohms
    b. 1,000 ohms + 1,000 Ohms = 2,000 Ohms
    c. 500 Ohms + 500 Ohms = 1,000 Ohms
    d. 500 Ohms + 250 Ohms = 750 Ohms

    Obviously, none of these answers match the 500 Ohms we need. So the resistors are connected in parallel. Let us find out which 2 resistors are in parallel. Without doing much calculations like for series, when 2 resistors of the same value are connected in parallel we can do a quick total resistance calculation method, which is basically dividing the resistance of 1 resistor by the total number of resistors in parallel (in this case 2). The only obvious choice is (b), because….

    1,000 Ohms / 2 = 500 Ohms.

    So the answer is (b).

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