Series Resistance and Ohm's Law
So far, we have learned that if two or more resistors are connected end to end,
they are in a SERIES circuit. We learned that the total resistance in a
series circuit is equal to the sum of the individual resistances. What we
didn't discuss, so far, was the relationship between Voltage, Current, and
Resistance in a circuit with multiple resistances.
If we examine our waterflow circuit, we find that any water which flows past
the 3rd valve, must first flow past the 2nd and 1st valves. By this we
can deduce that the current, or flow of water, is the same past all three
valves. At no time can more water flow past one valve than past another.
The same is true in electronics. In a SERIES circuit, the current is the same
at every point.
Using our previous example of 2
Ω
resistors, if we then have a 12 Volt source, what would be our current through
the circuit? Let us examine this. We know that because the circuit is series,
no matter where in the circuit we are, the current will remain the same. So
the problem is, what would be the given current for the complete circuits given
voltage and resistance totals? Adding up our 3 resistors, we come to 6
W
, and we know our Voltage is 12. So using Ohms Law, we derive this formula:
