Hello everybody!
I've been spending a lot of time with the study of Thevenin's theorem, but have some misunderstanding on this topic. It is caused by a contradiction between two things.
On one side there is an electrical textbook's lesson and my experiment.
On the other side there is the writing of the All about circuit page (http://www.allaboutcircuits.com/vol_1/chpt_10/8.html), and I can not solve the problem.
All about circuit says at the 4. figure, that:
"the original circuit with the load resistor removed is nothing more than a simple series circuit with opposing batteries, and so we can determine the voltage across the open load terminals by applying the rules of series circuits, Ohm's Law, and Kirchhoff's Voltage Law".
Later, it concludes that the total Voltage is 21V.
However, another electronic textbook says that the parallel wired generators are built by connecting the same poles together (+ to +, - to -). Based upon this, I think that the resistances are really in series with each other, but the batteries are not. On the 4. figure they are wired together parallel, so the total Voltage should be 28V, or in real life near 28V (at least based on my reasoning)!
I checked this with my own experiment. I have a breadboard, and two batteries. One has still 9V, but the other one is quite old, has only 4.6V but the same design, other words it used to be a 9V battery as well. I connected them together using the same polarities. I mean, I wired the + polarity to the +, the - to the - (but I didn't shortcircuit them! Actually, I left open the circuit). Then I measured the voltage on the battery's main poles. The voltage was the same on both batteries (aroung 8.3V), doesn't matter which battery I've chosen to measure.
So the batteries doesn't seem to reduce their voltage just because they are connected together on the same poles.
Is it possible that the above mentioned page has a fault with the calculation (at total voltage, which should not be 21V rather 28V)?
I've been spending a lot of time with the study of Thevenin's theorem, but have some misunderstanding on this topic. It is caused by a contradiction between two things.
On one side there is an electrical textbook's lesson and my experiment.
On the other side there is the writing of the All about circuit page (http://www.allaboutcircuits.com/vol_1/chpt_10/8.html), and I can not solve the problem.
All about circuit says at the 4. figure, that:
"the original circuit with the load resistor removed is nothing more than a simple series circuit with opposing batteries, and so we can determine the voltage across the open load terminals by applying the rules of series circuits, Ohm's Law, and Kirchhoff's Voltage Law".
Later, it concludes that the total Voltage is 21V.
However, another electronic textbook says that the parallel wired generators are built by connecting the same poles together (+ to +, - to -). Based upon this, I think that the resistances are really in series with each other, but the batteries are not. On the 4. figure they are wired together parallel, so the total Voltage should be 28V, or in real life near 28V (at least based on my reasoning)!
I checked this with my own experiment. I have a breadboard, and two batteries. One has still 9V, but the other one is quite old, has only 4.6V but the same design, other words it used to be a 9V battery as well. I connected them together using the same polarities. I mean, I wired the + polarity to the +, the - to the - (but I didn't shortcircuit them! Actually, I left open the circuit). Then I measured the voltage on the battery's main poles. The voltage was the same on both batteries (aroung 8.3V), doesn't matter which battery I've chosen to measure.
So the batteries doesn't seem to reduce their voltage just because they are connected together on the same poles.
Is it possible that the above mentioned page has a fault with the calculation (at total voltage, which should not be 21V rather 28V)?