(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

The circuit in the attached figure (excuse the terrible drawing, I suck at using the paint feature) all meters are idealized and the batteries have no appreciable internal resistance

a) Find the reading of the voltmeter with the switch S open

b) With the switch closed, find the reading of the voltmeter and the ammeter. Which way does the current flow through the switch?

2. Relevant equations

V = I/R (ohm's law)

[tex]\Sigma[/tex]I = 0 (junction law)

[tex]\Sigma[/tex]V = 0 (loop law)

3. The attempt at a solution

To find the reading of the voltmeter I attempted to find the currents going through the 2 emf's and then using the junction rule to find current at point a (the top) and then using ohm's law with that current and the 75 ohm resistor to find the reading of the voltmeter, with the switch open I treated that segment as if the switch line wasn't there, here's what I got

for loop 1 (with the 25V emf)

25V-I1(100 ohms) = 0

25V = I1(100ohms), I1 = .25A

for loop 2 (with the 15V emf)

15V-I2(75 ohms) = 0

15V = I2(75 ohms), I2 = .20A

junction rule .25A-.20A-I = 0, I = .05A

ohm's law for voltmeter

I = V/R, V = IR -> V = (.05A)(75ohms) = 3.75V

I'm not sure if I did the question correctly, if any one can check it for me I would appreciate it, thank you.

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# Homework Help: Reading of a Voltmeter

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