1. University Physics: Waves and Electricity
Lecture 11
Ch27. Circuit Theory
University Physics: Waves and Electricity
Dr.-Ing. Erwin Sitompul
2016

2. Homework 10
Find the equivalent resistance between points a and b in the circuit diagram below.
Calculate the current in each resistor if a potential difference of 34 V is applied between points a and b.

3. Solution of Homework 10
(a)
(b) ≡

4. Solution of Homework 10 c d ≡ c d

5. Example: Single-Loop Circuit
For the circuit shown, determine Vab.
a ® a, cw i
a ® b, ccw
Try again for i assumed to be ccw
Assume a current direction
Perform the calculation
i > 0 means that the current flows in the assumed direction
i < 0 means that the current flows in opposite direction

6. Voltage Divider and Current Divider

7. Req of Two Resistance in Parallel

8. Example: Finding Voltage and Current
For this circuit, determine i1, i2, V1, and V2. ≡

9. Example: Two-Loop Circuit
If E1 = 20 V, determine E2 and E3. 1
Loop 1, cw 2
Loop 2, cw
Outer Loop, ccw

10. Multiloop Circuits
Junction Rule: The sum of the currents entering any junction must be equal to the sum of the currents leaving that junction
Remember again Loop Rule, Resistance Rule, and Emf Rule
Our basic tools for solving complex circuits are the loop rule and the junction rule.
Junction Rule, at d
(1)
Loop Rule, left-hand loop, b ® b, ccw
(2)
Loop Rule, right-hand loop, b ® b , ccw
(3)
Afterward, find the unknowns from these three equations

11. Example: Multiloop Circuits
The value of the elements in the following circuits are:
E1 = 3 V, E2 = 6 V,
R1 = 2 Ω, R2 = 4 Ω
Find the magnitude and direction of the current in each of the branches.
Junction Rule, at a
(1)
Loop Rule, left-hand loop, a ® a, ccw
Loop Rule, right-hand loop, a ® a , cw
. . .(2)
. . .(3)

12. Example: Multiloop Circuits
(1)
Option B: Substitution Method
. . .(2)
From (2)
. . .(3)
(5)
Insert (1) into (3),
Insert (5) into (4)
. . .(4)
Option A: Elimination Method

13. Homework 11
For the circuit depicted below, determine the currents (i1, i2, i3) and the potential difference across the resistors (V1, V2, V3).

14. Homework 11A
For the circuit depicted on the right side, determine the currents (i1, i2, i3) and the potential difference across the resistors (V1, V2, V3).
For the circuit shown by the figure on the right, determine Vcb and i7.0 Ω.