Final answer:
In a parallel circuit, the main line connects all the branches to the terminals of the voltage source and carries the total current from the source. The voltage across each branch remains the same, but the current splits based on the resistance of each branch.
Step-by-step explanation:
In a parallel circuit, the pair of leads connecting all the branches to the terminals of the voltage source is called the main line. The main line carries the total current from the voltage source and distributes it to the different branches of the circuit. The voltage across each branch in a parallel circuit remains the same, but the current splits based on the resistance of each branch.
For example, if we have a parallel circuit with three branches, each branch will have a different resistance. However, the voltage across each branch will be the same because they are all connected to the same terminals of the voltage source. The main line carries the total current from the voltage source and divides it into the different branches.