Well, we all know that in a voltage Divider circuit like this, Output voltage is: (R2xV1)/(R1+R2)

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Can someone tell me how do you go about finding voltage in this?

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I want to find out voltage between Point A & B, and then the voltage between A & C?

  • \$\begingroup\$ Just curious: Is this a crude PC fan speed lowering circuit? Just asking, as 3.5V might be too low to turn the fan on. (not ot mention the resistors lowering it even more as the fan would draw current through the resistor) \$\endgroup\$
    – ppeterka
    Sep 15, 2013 at 9:15
  • \$\begingroup\$ No It is not, i was just looking at a circuit, and was confused at some point. \$\endgroup\$
    – Sherby
    Sep 15, 2013 at 16:30
  • \$\begingroup\$ so many approaches can be done. Apply KVL in series circuit with "C" common node. Current in series circuit is 7/100, voltage across R2 = 100*7/200 = 3.5V. \$\endgroup\$
    – user19579
    Sep 17, 2013 at 11:46

1 Answer 1


This one can be solved by inspection. Notice that the 5V source is in series with the 12V source but oriented in the opposite direction. So, the voltage across both resistors is just 7V. You could use the voltage divider equation again to find the voltage from A to B, but since the resistors have the same value the voltage across each of them must also be the same. So the voltage across A and B is 3.5V, with A being the more positive point. Now the voltage between C and A is just the sum of the voltages from C to B and then from B to A.


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