Question

What circuits do KCL and KVL apply to?

Answer 1

Kirchhoff's Current Law (KCL) and Kirchhoff's Voltage Law (KVL) apply to any electrical circuit—whether it's a simple series or parallel circuit, or a more complex one. Here’s a breakdown of each:

1. Kirchhoff's Current Law (KCL):

1. Applies to: Junctions or nodes in a circuit.
   

1. What it says: The total current entering a node (or junction) must be equal to the total current leaving that node. In other words, the sum of currents at a node is zero.
   

1. Where it applies: This law is valid for all circuits, whether AC or DC, as long as we are considering the point where currents meet (a node).
   

Example:

Imagine a junction where three wires meet. If 5 A of current enters the node, and two wires carry 3 A and 2 A of current away, KCL tells us that the sum of all currents at the node is zero:  
5 A entering = 3 A + 2 A leaving.

2. Kirchhoff's Voltage Law (KVL):

1. Applies to: Loops or closed paths in a circuit.
   

1. What it says: The sum of all voltages around any closed loop (or mesh) in a circuit is zero. This means the sum of the voltage rises (like across batteries) equals the sum of voltage drops (like across resistors).
   

1. Where it applies: KVL applies to all circuits as long as the loop is closed, including circuits with resistors, capacitors, inductors, and voltage sources.
   

Example:

Consider a loop with a battery (providing 12 V) and two resistors. If the total voltage drop across the resistors is 12 V, KVL tells us that:  
Voltage rise from the battery (12 V) = Voltage drops across resistors (12 V).  

In short:

1. KCL applies at any node where currents meet.
   

1. KVL applies around any closed loop in the circuit.
   

These laws are fundamental and hold true for all circuits, including DC, AC, linear, and non-linear circuits.