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Zef:
You need a book on electrical circuit theory. Start with simple DC circuits.
I will try to explain several points.
when a circuit completes itself it comes back on the neutral at 120v but why when you land the neutral on the neutral buss bar nothing happens?
What exactly were you asking here? I am not sure.
Consider a very simple circuit.
http://en.wikipedia.org/wiki/Series_and_parallel_circuits
At the beginning of the article is a simple series circuit of a battery and three resistors in series. Consider the top resistor to be your hot wire , the right hand resistor the load , and the bottom or your neutral wire.
Use the bottom end of the battery as ground, your neutral bus bar, and a reference point for voltage measurements.
Assume the battery is 10 V. Assume the top and bottom resistors are 0.1 ohms, and the right hand resistor is 9.8 ohms.
Open the connection at the top (+) end of the battery. Measure the voltage across the battery. This will be 10 V. Measure the voltage from the negative end of the battery to any other point in the circuit and the voltage will be 0 V.
Reconnect the top resistor to the + battery terminal.
What is the current flow in the circuit? I = V/R = 10 / (0.1 + 9.8 + 0.1) = 10 / 10 = 1 A.
Relative to the battery negative end what is the voltage at each point in the series circuit? 10.0, 9.9, 0.1, 0.0 .
Next open the lower right corner. What is the voltage at the right end of the bottom resistor? 0.0 V. What is the voltage at the bottom end of the right resistor? 10.0 V.
Reconnect the lower right corner, open the connection of the bottom resistor to the negative end of the battery. What is the voltage of the left end of the bottom resistor? 10.0 V. What is the voltage of the bottom end of the right resistor? 10.0 V. If this were a 120 V circuit and you touched one hand on the negative end of the battery and the other hand on the neutral wire you would get a severe shock, and maybe kill yourself.
Now suppose the right hand resistor is infinite, an open circuit for the load. What is the voltage at the right hand end of the bottom resistor (your neutral)? 0.0 V. Same at the left hand end.
Can you start to see what happens in the circuit of your original post?
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