# Electronic exam

Discussion in 'Electronics Homework Help' started by AlexMihai, Feb 13, 2012.

1. ### AlexMihai

2
0
Feb 13, 2012
Yesterday i had exam at electronics and i failed at it, the reason was i didn't know how to solve correctly electric circuits. Our exam contains 2 theories and 2 circuits electric problem, one is a continuous circuit and the other a alternative circuit.

At the continuous circuit problem we solve with the kirchoff theories, we determine the number of sides, nodes and independent curls(topological analysis). We apply Theory 1 of Kirchoff to the number of (nodes-1) and Theory 2 of Kirchoff to the curls, from there apllications we obtain a ecuation system which we must solve in order to determine the currents and voltages at the terminals (e.g. A, B). The ways of currents which goes to the node inside/outside which we apply on the circuit on the first step is random. If the results of the ecuation system are negative values we must revert the current way which is pointing to the the node.

The method i pretty much understand it but i made a mistake which ruined the rest of the problem i solved and heres why:
We had this circuit and someones told me that the elements on the line of the conductors(which has a switch control) must be cut and also the circuit must be disconnected from the source?
I didn't understand the last part which i must do about disconneting it from the sources and how the circuit will look after this in order to apply the Kirchoff methods.

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Last edited: Feb 13, 2012
2. ### Raven Luni

798
8
Oct 15, 2011
The source is the source of power. Its difficult from that diagram to see where the switch is. Is that it at the top middle? If so then even when it is off you would still have a closed circuit with 3 resistors and a capacitor. The switch needs to be directly connected to the power source with no other lines bypassing it.

p.s. Can I put that drawing on my fridge?

3. ### Harald KappModeratorModerator

11,986
2,808
Nov 17, 2011
It sounds a bit confused. Maybe what is menat is this:
If you have multiple sources in a circuit, you can analyze the circuit by removing all but one source, the solving for this source. Then remove this source and add one of the sources you removed in the first step. Solve again. Do this for all sources. Then add the results of your calculations.
But be careful: any removed voltage source must be replaced by a short cuircuit, any removed current source must be replaced by an open circuit.
You can read it up here: http://en.wikipedia.org/wiki/Superposition_theorem

Harald

4. ### AlexMihai

2
0
Feb 13, 2012
Hello, sorry for the 'funny' circuit, here's how the circuit was looking

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