Kirchhoff's Laws are two fundamental principles that govern how current and voltage behave in circuits. Named after German physicist Gustav Kirchhoff, these laws are essential for analyzing complex circuits.
Our circuit simulator uses these laws to calculate realistic behavior in your designs!
The Law:
The sum of all currents entering a node equals the sum of all currents leaving that node.
Σ I_in = Σ I_out
In simple terms: Current can't just disappear or appear out of nowhere. Whatever flows into a junction must flow out of it.
Example:
If 100mA flows into a junction and splits into two branches, maybe 60mA goes down one path and 40mA down the other. The total out (60mA + 40mA) equals the total in (100mA).
The Law:
The sum of all voltage rises and drops around any closed loop in a circuit equals zero.
Σ V_loop = 0
In simple terms: The voltage supplied by the power source equals the sum of all voltage drops across components in the loop.
Example:
A 9V battery powers two resistors in series:
The voltage drops (9V) equal the voltage rise from the battery (9V)!
Let's analyze a circuit with a 5V battery, a 220Ω resistor, and a red LED in series:
Step 1: Apply KVL around the loop
V_battery = V_resistor + V_LED
5V = V_resistor + 1.8V
V_resistor = 3.2V
Step 2: Use Ohm's Law to find current
I = V_resistor / R = 3.2V / 220Ω = 14.5mA
Step 3: Verify with KCL
Since this is a series circuit, the same 14.5mA flows through the battery, resistor, and LED. KCL is satisfied at every junction!