No credit will be given for answers without appropriate supporting work. Minimum

Question

No credit will be given for answers without appropriate supporting work. Minimum good presentation requires the following: (1) Symbolic expression for any formula, (2) Manipulation of symbolic expressions, not numeric expressions, (3) Substitution of numbers with units, (4) Reporting final answers with correct units and vector expressions, (5) Enough English description to allow the reader to have some idea what you are doing without looking at the math.

Open-Response Homework Problem 8.2 For the circuit to the right, with R1 = 100?, R2 = 200?, and R3 = 300?, and ?V0 = 10V . (a)What is the equivalent resistance between points a and b? (b)What is the current drawn by the circuit? (c)What is the voltage drop across R1?

Explanation / Answer

Resistor R1 and R2 are in series so

equivalent resistance of R1 and R2 = R12 = R1 + R2

now R12 and R3 in parallel so equivalent resistance of circuit

Req = R12*R3/(R12 + R3)

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

Req = (100 + 200)*300/(100 + 200 + 300) = 150 ohm

b)

current drawn by the circuit = I = V0/Req = 10/150 = 0.066 amp

c)

current through R1 = I1 = I*R3/(R1 + R2 + R3) = 0.066*300/(100 + 200 + 300) = 0.033 amp

voltage drop across R1 = V1 = I1*R1

V1 = 0.033*100 = 3.3 volt

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