boylistad

Th
Conclusion:
5. Draw the Norton equivalent circuit with the portion of the circuit
previously removed replaced between the terminals of the
equivalent circuit.
The Norton and Thévenin equivalent circuits can also be found from
each other by using the source transformation discussed earlier in this
chapter and reproduced in Fig. 9.59.
RTh = R
+
N
ETh = INRN –
I N
ETh RTh R N = R Th
FIG. 9.59
Converting between Thévenin and Norton equivalent circuits.
EXAMPLE 9.11 Find the Norton equivalent circuit for the network in
the shaded area of Fig. 9.60.
Solution:
Steps 1 and 2 are shown in Fig. 9.61.
E
R 1
3 �
+
9 V
–
R 2
FIG. 9.61
Identifying the terminals of particular interest for the network of Fig. 9.60.
Step 3 is shown in Fig. 9.62, and
(3 �)(6 �) 18 �
RN � R1 �� R2 � 3 � �� 6 ���� �� �2 �
3 ��6 �
9
Step 4 is shown in Fig. 9.63, clearly indicating that the short-circuit
connection between terminals a and b is in parallel with R2 and eliminates
its effect. IN is therefore the same as through R1, and the full battery
voltage appears across R1 since
V2 � I2R2 � (0)6 ��0 V
Therefore,
E 9 V
IN �����3 A
R1 3 �
6 �
a
b
E
NORTON’S THEOREM ⏐⏐⏐ 339
R 1
3 �
+
9 V
–
R 2
6 �
FIG. 9.60
Example 9.11.
R 1
3 �
R 2
6 �
a
b
R N
FIG. 9.62
Determining R N for the network of Fig. 9.61.
I 1
R 1
I N
E
+
9 V
–
3 �
+
V2 R2 –
Short circuited
6 �
I N
I 2 = 0
a
b
Short
a
I N
b
R L
FIG. 9.63
Determining I N for the network of Fig. 9.61.