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November 4th, 2007, 02:38 AM   #1
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Electricity

We know that in a circuit the current through the resistor is the same as the current through the rest of the circuit.But the resistor offers resistance to the flow of current.It retards the flow of current.This being so, how can the current through the resistor be the same as the current through the rest of the circuit.
Can anyone give a clear explanation to this problem?
Also in a circuit where 2 resistors are connected in parallel why is the potential difference across each resistor the same?
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November 4th, 2007, 04:07 AM   #2
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In series the current is the same all the way through. Ohm's Law is that Voltage = Current * Resistance so with a constant voltage the higher the resistance the lower the current in the whole circuit.

I'm afraid I don't quite understand your second question

Hope that helps
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November 4th, 2007, 08:48 AM   #3
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The short answer to both questions is this: You use voltage division in a series circuit, and current division is a parallel circuit.

Let me explain: In a series circuit, voltage drops across each component as you go along, until you reach ground, which has 0 volts of relative potential. Current is not changed. The resistance effects the current, but only in the sense that more total resistance means less total current. The reason that the current does not drop across each resistor is that the current is a function of the TOTAL resistance, and thus putting in a bigger resistor will not cause the current to drop more across that resistor, but will instead cause the current to drop equally through the whole circuit.

In a parallel circuit, voltage must still drop across components until it reaches the 0 potential point of ground, but if you have several branches to the circuit, (thus making it parallel) then the same voltage is being applied to each branch. Thus, the same voltage must be dropped across each branch to reach 0 on the other end of each branch, the ends of which are all tied together again at ground. The difference in a parallel circuit is that current, while not changing because of voltage drops, does get split between all the different parallel lines, and as a result, the current is split in direct inverse proportion to the resistances in those lines. If the line has a high resistance, it has a low current, and vice versa. So, in a parallel circuit, resistance does effect the level of current, but in a slightly different way than it would in a series circuit.
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