CLASS 12 PHYSICS
Kirchhoff’s Laws — Clean English Notes
Topic: Circuit laws and applications Level: Class 12 / Higher Secondary
1. Kirchhoff’s Current Law (KCL)
Statement: At any junction (node) of an electrical circuit, the algebraic sum of currents is zero.
ΣI = 0
For the junction shown, taking currents entering the junction as positive and currents leaving it as negative:
Junction / Node
I■
I■ I■
I■
I■ + I■ − I■ − I■ = 0
Therefore, I■ + I■ = I■ + I■
Key idea
• The total current entering a junction is equal to the total current leaving it.
• KCL follows from the principle of conservation of charge.
• It is useful for finding unknown currents in complex electrical circuits.
2. Kirchhoff’s Voltage Law (KVL)
Statement: In any closed loop of an electrical circuit, the algebraic sum of all potential differences (voltage
changes) is zero.
Σ∆V = 0
R I
Potential drop = IR
10 V source
Class 12 Physics • Kirchhoff’s Laws • Page 1
Kirchhoff’s Laws — Clean English Notes
Topic: Circuit laws and applications Level: Class 12 / Higher Secondary
1. Kirchhoff’s Current Law (KCL)
Statement: At any junction (node) of an electrical circuit, the algebraic sum of currents is zero.
ΣI = 0
For the junction shown, taking currents entering the junction as positive and currents leaving it as negative:
Junction / Node
I■
I■ I■
I■
I■ + I■ − I■ − I■ = 0
Therefore, I■ + I■ = I■ + I■
Key idea
• The total current entering a junction is equal to the total current leaving it.
• KCL follows from the principle of conservation of charge.
• It is useful for finding unknown currents in complex electrical circuits.
2. Kirchhoff’s Voltage Law (KVL)
Statement: In any closed loop of an electrical circuit, the algebraic sum of all potential differences (voltage
changes) is zero.
Σ∆V = 0
R I
Potential drop = IR
10 V source
Class 12 Physics • Kirchhoff’s Laws • Page 1
