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I am having a bit of a tough time understanding the following:

|____O____| <-  0A
|____O____| <- 12A
|____O____| <- 24A
|         | <- 36A
|_[|||||]_| <- 36A


Legend:

O       - A small lamp with 1Ω resistance.
[|||||] - A 12V battery.

There is 12V flowing across each of the lamps and with resistance of 1Ω, and, therefore, there is 12 Amps of current flowing across each one. So, if the current is flowing from right side, up, over and down the left side, there is a total of 36 Amps flowing through the battery itself to supply the three connected lamps. At the top portion of either side of the top lamp (above the points where middle lamp connects) there is only 12 Amps of current; to either side of the middle lamp (above the points where the bottom lamp connects) there is 24 Amps; and to either side of the bottom lamp (below the points where the bottom lamp connects) there is 36 Amps.

Does it mean that a battery that could not shock us, could in fact if we connected several lamps in parallel circuit to raise the amount of current flowing through the circuit at the bottom portion? I'm just trying to wrap my head around circuits and electricity and this popped into my head. I've looked around, but couldn't find a clear answer to help me understand.

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1 Answer 1

up vote 2 down vote accepted

The analogy is wrong. A voltage source can only shock us if it is able to pass a considerable amount of current through our body ( ~ 250 mA or so, I dont know the exact value but you can Google it ). The circuit that you are trying to discuss, does indeed have 36 Amps of current flowing through it, but once you connect yourself to the circuit, you are in fact adding an additional resistance to the circuit (resistance of our body is usually within 100 - 150 k-ohms). This additional resistance will dramatically reduce the value of current in the circuit. All the potential difference will now drop across the high resistance, and very small amount would be leftover to the parallel resistors. With some rough values, there maybe approximately about 0.008 mA which is definitely not enough to be felt by a human being.

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Thank you for that answer. Well, I'm glad that I got the current part right at the very least. :) –  B.K. Dec 1 '13 at 9:00

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