The Parallel Circuit

So you want to dig a little deeper into the makings of the Parallel circuit...

Well let's get our shovels.... No forget the shovels....
Let's look at our Parallel Circuit from the last page.

We saw that when we connected the lights in
parallel that both could be bright, not dim like they
were when we connected them in series. That was
because unlike the series circuit, the full battery
voltage was connected across each light bulb.

Remember Kirchoff's Second Law? We added the voltage drops in the path and it equaled the
voltage coming from the battery. But here there are two paths so we must add each one
separately. Since there is only one light in each path, we can't add them together.

So each bulb has to have the full 1.5 Volts applied to it to satisfy Kirchoff's Second Law.
Another way of stating that is the Voltage across each load is always the same in a parallel circuit.

But this raises an interesting observation. The amount of light given off by both bulbs
is representative of the total amount of power being given off by the circuit.
We know the voltage across each light is the same as it was in the simple series circuit
with one light bulb, yet the amount of light is twice as much. Since the amount of light
has increased, and the voltage is the same, something else must also have changed.

The answer is the total amount of CURRENT has increased. This
is an important fact regarding parallel circuits. Just as in a series circuit
where the sum of all the voltage drops must equal the source voltage, in a
parallel circuit the sum of the current through each branch will equal
the total current flow in the circuit.

In other words, if the light in the first branch draws 1 amp and the light in
the second draws 2 amps, then the total current from the battery will equal 3 Amps.

Back to the Previous Page © JAN. 2007 - J. Brown