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Homework Help: Resistances in Series, Parallel, and Series-Parallel Combinations

  1. Feb 5, 2008 #1
    A 120-V circuit has a circuit breaker rated to trip (to create an open circuit) at 15 A. How many 300-ohm resistors could be connected in parallel without tripping the breaker?

    Given that,
    V= 120V, I = 15A, R= 300 ohm.
    Let the total resistance without tripping the breaker = Rp
    Now 1/Rp = 1/R + 1/ R + ………n times.
    = n/R
    Therefore Rp = R/n
    Or n = R/ Rp
    But Rp = 120/15
    = 8
    Therefore n = 300/8
    = 37.5=38

    Is this correct?
  2. jcsd
  3. Feb 6, 2008 #2
    No, because it will break on the 38th resistor. You want the one before **** hits the fan, the one right before the circuit breaks.
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