Glossary
Capacitance (negligible at junction)
A measure of a component's ability to store electric charge. For Kirchhoff's Junction Rule, 'negligible capacitance at junction' means no significant charge accumulates or depletes at the junction itself.
Example:
For Kirchhoff's Junction Rule to hold true even with changing currents, the wires forming the junction must have negligible capacitance, meaning they don't store or release charge themselves.
Charge Conservation
A fundamental principle in physics stating that the total electric charge in an isolated system remains constant; charge can neither be created nor destroyed, only transferred.
Example:
The operation of a lightning rod relies on the principle of charge conservation, allowing excess charge from a lightning strike to be safely dissipated into the ground rather than accumulating.
Current (I)
The rate of flow of electric charge through a conductor, typically measured in Amperes (A).
Example:
If a smartphone charger delivers 2 Amperes of current, it means 2 Coulombs of charge are flowing through the cable every second.
Incoming Currents
Electric currents that flow towards and enter a specific junction in an electrical circuit.
Example:
In a parallel circuit, the total current from the power source splits into multiple incoming currents for each branch connected to the first junction.
Junction (in circuits)
A point in an electrical circuit where three or more conductors or branches meet, allowing electric current to split or combine.
Example:
In a household wiring system, a light switch often acts as a junction, connecting or disconnecting the circuit path to the light fixture.
Kirchhoff's Junction Rule
A fundamental principle stating that the sum of electric currents entering any junction in a circuit must equal the sum of currents leaving that junction, reflecting the conservation of charge.
Example:
When analyzing a complex circuit, applying Kirchhoff's Junction Rule at a point where three wires meet allows you to determine an unknown current if the other two are known.
Outgoing Currents
Electric currents that flow away from and leave a specific junction in an electrical circuit.
Example:
After passing through parallel resistors, the individual branch currents recombine to form a single outgoing current at the next junction, equal to the total current that entered the parallel section.