A 5.2 MΩ resistor, 1.2 MΩ resistor and 1 MΩ resistor are connected in parallel across a 15 V source. What is the total current if the 1.2 MΩ resistor opens?
A)17.9 µA
B)12.5 µA
C)2.88 µA
D)2.41 µA

Question

Quizplus · Accepted Answer

The total resistance of the circuit is:1/Rt = 1/R1 + 1/R2 + 1/R31/Rt = 1/5.2 MΩ + 1/1.2 MΩ + 1/1 MΩRt = 0.68 MΩThe total current is:It = V/RtIt = 15 V / 0.68 MΩIt = 22.06 µAWhen the 1.2 MΩ resistor opens, the total resistance becomes:1/Rt' = 1/R1 + 1/R31/Rt' = 1/5.2 MΩ + 1/1 MΩRt' = 0.85 MΩThe total current becomes:It' = V/Rt'It' = 15 V / 0.85 MΩIt' = 17.65 µATherefore, the total current if the 1.2 MΩ resistor opens is 17.65 µA, which is closest to choice A) 17.9 µA.

A 52 MΩ Resistor, 1