Splitting Currents
In this lesson, we are going to talk about how currents split in circuits. You may remember
from Mr. Liechty’s video that he drew the following circuit:
Dr. Marshall also built a similar circuit in her video. As both experts explained, the current will
split evenly between the two possible paths and so each light will get half of the current that
comes out of the battery. Therefore, the bulbs have the same brightness.
As the experts explained, the current splits equally because both of the paths have the same
resistance (since the two bulbs are identical).
Suppose that to one of the paths, we add a resistor like shown:
Now the left hand path has more resistance than the right hand path. As a result, more current
will flow through the right hand path and less will flow through the left hand path. Therefore,
the bulb on the left (which gets less current) will be dimmer than the bulb on the right.
The bigger the resister is, the harder it will be for current to flow through the left hand path and
the dimmer the bulb on the left will be.
At the extreme, suppose that we removed the bulb on the right completely:
You might remember Dr. Marshall building a circuit like this one in her video. As she explained,
the right hand path has no resistance whatsoever. As a result, all of the current will flow
through that path and none will flow through the path on the left. Therefore the bulb will not
be lit at all (and the battery will get very hot like it did when Dr. Marshall connected both ends
with a wire; depending on the exact type of battery and the exact wire, building a circuit like
this one can be dangerous).