kris2c
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----------R1---------------
----------R2---------------
100mmHg --> ----------R3--------------- --> 10mmHg
----------R4---------------
----------R5---------------
R1=R2=R3=R4=R5= 5mmHg/mL/min
Blood is flowing through the circuit shown above. The inflow pressure is 100 mm Hg and the outflow pressure is 10 mm Hg. The resistance of each of the five branches is 5 mm Hg/mL/min. What is the flow across the circuit?
A. 3.6 mL/min
B. 45 mL/min
C. 90 mL/min
D. 135 mL/min
E. 180 mL/min
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| peekay
Forum Guru
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E- -----------(flow=change in pressure/resistence)
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| kris2c
Forum Senior
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the Rs are in parallel, the Pin=100 and Pout= 10
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| krsma
Forum Elite
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A?
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| cprax
Forum Junior
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Is it C?
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| kris2c
Forum Senior
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The correct answer is C.
Because the various resistances (R1-R5) are arranged in parallel, the total resistance of the circuit (RT) is calculated using the following formula:
1/RT = 1/R1 + 1/R2 + 1/R3 + 1/R4 + 1/R5
Therefore, the resistance of the circuit is
1/ RT = 1/5 + 1/5 + 1/5 + 1/5 +1 /5 = 1 mm Hg/mL/min.
Because flow = Δ pressure/resistance, the total flow through the circuit is (100 - 10 mm Hg)/1 mm Hg/mL/min = 90 mL/min.
Note from the equation that the total resistance (RT) decreases when additional resistances are added in parallel to the circuit. Conversely, the total resistance increases when parallel resistances are removed. Because the various organs of the body are arranged in parallel, the total peripheral resistance increases when an organ is removed.
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