Unit 9
Kirchhoff's Law, Thevenin’s, Norton’s,
and Superposition Theorems
Kirchhoff’s Laws
1. The algebraic sum of the voltage sources
and voltage drops in a closed circuit must
equal zero.
2. The algebraic sum of the current entering
and leaving a point must equal zero.
Unit 9
Kirchhoff's Law, Thevenin’s, Norton’s,
and Superposition Theorems
Kirchhoff’s Current Law
“The algebraic sum of the current entering
and leaving a point must equal zero.”
This law is for parallel circuits and states
that the total current is the sum of all of the
branch currents.
Unit 9
Kirchhoff's Law, Thevenin’s, Norton’s, and
Superposition Theorems
Kirchhoff’s Current Law
The algebraic sum of the currents entering and
leaving a point must equal zero
Unit 9
Kirchhoff's Law, Thevenin’s, Norton’s,
and Superposition Theorems
Kirchhoff’s Voltage Law
“The algebraic sum of the voltage
sources and voltage drops in a closed
circuit must equal zero.”
This law states that the sum of the
voltage drops in a series circuit must
equal the applied voltage.
Unit 9
Kirchhoff's Law, Thevenin’s, Norton’s,
and Superposition Theorems
Kirchhoff’s Voltage Law
“The algebraic sum of the voltage sources
and voltage drops in a closed circuit must
equal zero.”
This law states that the sum of the voltage
drops in a series circuit must equal the
applied voltage.
Unit 9
Kirchhoff's Law, Thevenin’s, Norton’s, and
Superposition Theorems
Kirchhoff’s Voltage Law
The algebraic sum of the voltages around any closed loop must equal zero.
Unit 9
Kirchhoff's Law, Thevenin’s, Norton’s,
and Superposition Theorems
Thevenin’s Theorem
Thevenin’s theorem simplifies a circuit into
an equivalent circuit which contains a single
voltage source and series resister.
Unit 9
Kirchhoff's Law, Thevenin’s, Norton’s, and
Superposition Theorems
Thevenin’s Theorem
The equivalent Thevenin Circuit consists of a single power source and single
series resistor.
Unit 9
Kirchhoff's Law, Thevenin’s, Norton’s,
and Superposition Theorems
Norton’s Theorem
Norton’s Theorem is used to reduce a
circuit network into a simple current source
and a single parallel resistance.
Unit 9
Kirchhoff's Law, Thevenin’s, Norton’s,
and Superposition Theorems
Norton’s Theorem
Unit 9
Kirchhoff's Law, Thevenin’s, Norton’s, and
Superposition Theorems
Superposition Theorem
Any branch of a circuit supplied by a multipower
source can be determined by finding the current
produced in that particular branch by each of the
individual power sources acting alone. All other
power sources must be replaced by a resistance
equivalent to their internal resistances. The total
current flow through the branch is the algebraic sum
of the individual currents produced by each of the
power sources.
Unit 9
Kirchhoff's Law, Thevenin’s, Norton’s,
and Superposition Theorems
Superposition Theorem