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This was one of my assignment questions, I am on it since last 3 hours but not able to solve it. Here the source voltage in the circuit shown in Fig. is 100 V.

I need to find reading in each meter. I don't know what I am doing wrong in applying KVL here. Please give your solution.

figure

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  • \$\begingroup\$ I'll give you a short answer: It's 100V across each resistor. \$\endgroup\$
    – Big6
    Commented Aug 14, 2016 at 5:48
  • \$\begingroup\$ can you please explain how? , I am more baffled now. Please add a brief explanation. \$\endgroup\$ Commented Aug 14, 2016 at 5:50
  • \$\begingroup\$ If you measure across each resistor, you're actually measuring across the source. Notice how the terminals of each resistor are connected to the source. \$\endgroup\$
    – Big6
    Commented Aug 14, 2016 at 5:57
  • \$\begingroup\$ I feel so dumb, got it now. Thanx \$\endgroup\$ Commented Aug 14, 2016 at 6:01

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This is actually (as you have noticed, with a face-palm) a trick question. It's designed to see how observant you are.

The circuit is laid out in such a way as to trick you into thinking it's more complex than it is. It isn't though - it can be better drawn out like this:

schematic

simulate this circuit – Schematic created using CircuitLab

You notice I have also turned the schematic upside down so + is at the top and - is at the bottom. You can now instantly see that the three resistors are just all in parallel with each other and therefore all in parallel with the 100V supply, making the voltage across each resistor 100V.

You have to remember that in a schematic all the nodes and "joins" that are linked together by a simple wire are effectively the same node. In the schematic above I have coloured a selection of wires in red. They are all the same wire - all the same node - and thus all at the same potential. It's only when you come to tracing the current flow through it that you start to split values between different branches.

So, \$V_{M1} = V_{M2} = V_{M3} = V_1\$ and \$I_{R1} = \frac{V_1}{R_1}, I_{R2} = \frac{V_1}{R_2}, I_{R3} = \frac{V_1}{R_3}\$

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