The Governing Equations of a Multi Loop Circuit

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The Laws
An Example
The Governing Equations of a Multi Loop
Circuit
Bernd Schröder
Bernd Schröder
The Governing Equations of a Multi Loop Circuit
logo1
Louisiana Tech University, College of Engineering and Science
The Laws
An Example
Kirchhoff’s Laws
Bernd Schröder
The Governing Equations of a Multi Loop Circuit
logo1
Louisiana Tech University, College of Engineering and Science
The Laws
An Example
Kirchhoff’s Laws
1. Kirchhoff’s Voltage Law. The sum of the voltages in a
closed loop is zero.
Bernd Schröder
The Governing Equations of a Multi Loop Circuit
logo1
Louisiana Tech University, College of Engineering and Science
The Laws
An Example
Kirchhoff’s Laws
1. Kirchhoff’s Voltage Law. The sum of the voltages in a
closed loop is zero.
1.1 It’s conservation of energy. If the sum was not zero, we
could indefinitely accelerate a charge by sending it around.
Bernd Schröder
The Governing Equations of a Multi Loop Circuit
logo1
Louisiana Tech University, College of Engineering and Science
The Laws
An Example
Kirchhoff’s Laws
1. Kirchhoff’s Voltage Law. The sum of the voltages in a
closed loop is zero.
1.1 It’s conservation of energy. If the sum was not zero, we
could indefinitely accelerate a charge by sending it around.
u
C C C CC
CC CC CC
X
X
X
X
X
X
X
X
O
X
X
X
C C C CC
CC CC CC
Bernd Schröder
The Governing Equations of a Multi Loop Circuit
∑ vloop = 0
logo1
Louisiana Tech University, College of Engineering and Science
The Laws
An Example
Kirchhoff’s Laws
1. Kirchhoff’s Voltage Law. The sum of the voltages in a
closed loop is zero.
1.1 It’s conservation of energy. If the sum was not zero, we
could indefinitely accelerate a charge by sending it around.
Bernd Schröder
The Governing Equations of a Multi Loop Circuit
logo1
Louisiana Tech University, College of Engineering and Science
The Laws
An Example
Kirchhoff’s Laws
1. Kirchhoff’s Voltage Law. The sum of the voltages in a
closed loop is zero.
1.1 It’s conservation of energy. If the sum was not zero, we
could indefinitely accelerate a charge by sending it around.
1.2 Careful with signs.
Bernd Schröder
The Governing Equations of a Multi Loop Circuit
logo1
Louisiana Tech University, College of Engineering and Science
The Laws
An Example
Kirchhoff’s Laws
1. Kirchhoff’s Voltage Law. The sum of the voltages in a
closed loop is zero.
1.1 It’s conservation of energy. If the sum was not zero, we
could indefinitely accelerate a charge by sending it around.
1.2 Careful with signs.
1.3 In loops with a source, we can also say that the sum of the
voltages on the elements is equal to the external voltage.
Bernd Schröder
The Governing Equations of a Multi Loop Circuit
logo1
Louisiana Tech University, College of Engineering and Science
The Laws
An Example
Kirchhoff’s Laws
1. Kirchhoff’s Voltage Law. The sum of the voltages in a
closed loop is zero.
1.1 It’s conservation of energy. If the sum was not zero, we
could indefinitely accelerate a charge by sending it around.
1.2 Careful with signs.
1.3 In loops with a source, we can also say that the sum of the
voltages on the elements is equal to the external voltage.
2. Kirchhoff’s Current Law. The sum of the currents into and
out of a node is zero.
Bernd Schröder
The Governing Equations of a Multi Loop Circuit
logo1
Louisiana Tech University, College of Engineering and Science
The Laws
An Example
Kirchhoff’s Laws
1. Kirchhoff’s Voltage Law. The sum of the voltages in a
closed loop is zero.
1.1 It’s conservation of energy. If the sum was not zero, we
could indefinitely accelerate a charge by sending it around.
1.2 Careful with signs.
1.3 In loops with a source, we can also say that the sum of the
voltages on the elements is equal to the external voltage.
2. Kirchhoff’s Current Law. The sum of the currents into and
out of a node is zero.
HH
j
H
HH
H
*
HH u
HH
H
H
H
H
jH
H
*
HH
H
Bernd Schröder
The Governing Equations of a Multi Loop Circuit
∑ iin = ∑ iout
logo1
Louisiana Tech University, College of Engineering and Science
The Laws
An Example
Kirchhoff’s Laws
1. Kirchhoff’s Voltage Law. The sum of the voltages in a
closed loop is zero.
1.1 It’s conservation of energy. If the sum was not zero, we
could indefinitely accelerate a charge by sending it around.
1.2 Careful with signs.
1.3 In loops with a source, we can also say that the sum of the
voltages on the elements is equal to the external voltage.
2. Kirchhoff’s Current Law. The sum of the currents into and
out of a node is zero.
Bernd Schröder
The Governing Equations of a Multi Loop Circuit
logo1
Louisiana Tech University, College of Engineering and Science
The Laws
An Example
Kirchhoff’s Laws
1. Kirchhoff’s Voltage Law. The sum of the voltages in a
closed loop is zero.
1.1 It’s conservation of energy. If the sum was not zero, we
could indefinitely accelerate a charge by sending it around.
1.2 Careful with signs.
1.3 In loops with a source, we can also say that the sum of the
voltages on the elements is equal to the external voltage.
2. Kirchhoff’s Current Law. The sum of the currents into and
out of a node is zero.
2.1 It’s conservation of mass. If the sum was not zero, charges
would either be created or destroyed at the node. (There is
no storage in conductors.)
Bernd Schröder
The Governing Equations of a Multi Loop Circuit
logo1
Louisiana Tech University, College of Engineering and Science
The Laws
An Example
Kirchhoff’s Laws
1. Kirchhoff’s Voltage Law. The sum of the voltages in a
closed loop is zero.
1.1 It’s conservation of energy. If the sum was not zero, we
could indefinitely accelerate a charge by sending it around.
1.2 Careful with signs.
1.3 In loops with a source, we can also say that the sum of the
voltages on the elements is equal to the external voltage.
2. Kirchhoff’s Current Law. The sum of the currents into and
out of a node is zero.
2.1 It’s conservation of mass. If the sum was not zero, charges
would either be created or destroyed at the node. (There is
no storage in conductors.)
3. Council’s Law (honorable mention). Never become part of
the circuit.
Bernd Schröder
The Governing Equations of a Multi Loop Circuit
logo1
Louisiana Tech University, College of Engineering and Science
The Laws
An Example
R1
s
B B B B B
B B B B B
PP
PP
R2 PP
PP
E(t)
C
qs
Bernd Schröder
The Governing Equations of a Multi Loop Circuit
logo1
Louisiana Tech University, College of Engineering and Science
The Laws
An Example
R1
s
node
B B B B B
B B B B B
PP
PP
R2 PP
PP
E(t)
C
qs
Bernd Schröder
The Governing Equations of a Multi Loop Circuit
logo1
Louisiana Tech University, College of Engineering and Science
The Laws
An Example
R1
i1
i2
B B B B B - sB B B B B
node
i3 ?
PP
PP
R2 PP
PP
E(t)
C
qs
Bernd Schröder
The Governing Equations of a Multi Loop Circuit
logo1
Louisiana Tech University, College of Engineering and Science
The Laws
An Example
R1
i1
i2
B B B B B - sB B B B B
node
i3 ?
PP
PP
R2 PP
PP
E(t)
C
qs
Bernd Schröder
The Governing Equations of a Multi Loop Circuit
i1 = i2 + i3
logo1
Louisiana Tech University, College of Engineering and Science
The Laws
An Example
R1
i1
i2
B B B B B - sB B B B B
node
i3 ?
PP
PP
R2 PP
PP
U
E(t)
loop
1
C
qs
Bernd Schröder
The Governing Equations of a Multi Loop Circuit
i1 = i2 + i3
logo1
Louisiana Tech University, College of Engineering and Science
The Laws
An Example
R1
i1
i2
B B B B B - sB B B B B
node
i3 ?
PP
PP
R2 PP
PP
U
E(t)
loop
1
C
qs
i1 = i2 + i3
E(t) =
Bernd Schröder
The Governing Equations of a Multi Loop Circuit
logo1
Louisiana Tech University, College of Engineering and Science
The Laws
An Example
R1
i1
i2
B B B B B - sB B B B B
node
i3 ?
PP
PP
R2 PP
PP
U
E(t)
loop
1
C
qs
i1 = i2 + i3
E(t) = R1 i1
Bernd Schröder
The Governing Equations of a Multi Loop Circuit
logo1
Louisiana Tech University, College of Engineering and Science
The Laws
An Example
R1
i1
i2
B B B B B - sB B B B B
node
i3 ?
PP
PP
R2 PP
PP
U
E(t)
loop
1
C
qs
i1 = i2 + i3
1
E(t) = R1 i1 +
C
Bernd Schröder
The Governing Equations of a Multi Loop Circuit
Z
i3 dt
logo1
Louisiana Tech University, College of Engineering and Science
The Laws
An Example
R1
i1
i2
B B B B B - sB B B B B
node
i3 ?
U
E(t)
loop
1
U
loop 2
R2
C
qs
PP
PP
PP
PP
i1 = i2 + i3
1
E(t) = R1 i1 +
C
Bernd Schröder
The Governing Equations of a Multi Loop Circuit
Z
i3 dt
logo1
Louisiana Tech University, College of Engineering and Science
The Laws
An Example
R1
i1
i2
B B B B B - sB B B B B
node
i3 ?
U
E(t)
loop
1
U
loop 2
R2
C
qs
PP
PP
PP
PP
i1 = i2 + i3
1
E(t) = R1 i1 +
C
R2 i2
Bernd Schröder
The Governing Equations of a Multi Loop Circuit
Z
i3 dt
logo1
Louisiana Tech University, College of Engineering and Science
The Laws
An Example
R1
i1
i2
B B B B B - sB B B B B
node
i3 ?
U
E(t)
loop
1
U
loop 2
R2
C
qs
PP
PP
PP
PP
i1 = i2 + i3
1
E(t) = R1 i1 +
C
Z
1
i3 dt
R2 i2 −
C
Bernd Schröder
The Governing Equations of a Multi Loop Circuit
Z
i3 dt
logo1
Louisiana Tech University, College of Engineering and Science
The Laws
An Example
R1
i1
i2
B B B B B - sB B B B B
node
i3 ?
U
E(t)
loop
1
U
loop 2
R2
C
qs
PP
PP
PP
PP
i1 = i2 + i3
1
E(t) = R1 i1 +
i3 dt
C
Z
1
i3 dt = 0
R2 i2 −
C
Z
Bernd Schröder
The Governing Equations of a Multi Loop Circuit
logo1
Louisiana Tech University, College of Engineering and Science
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