Experiment 4  Junctions and Loops in a Circuit
Circuits can be more complicated
than in the circuits from the last experiments.
They can have multiple branches...
Before you examine branched circuits and Kirchhoff's laws, you need
to be clear about some terms used...

At a junction at least three current paths meet.

A branch is the path that connects two junctions.

A loop is a closed path of a least two paths connecting at
least two junctions.
Circuit of a branched circuit.
(Enlarge) 
In the circuit shown you have introduced
two junctions
A and
B.
All three resistors heat now up
(Resistor R1 heats up much more than the other two resistors.).
Therefore, at the junction the current is divided and flows
through both resistors R2 and R3!
Circuit diagram branched circuit.
The conduct of the current at the junction is described
by the first Kirchhoff law...
