1. Chapter 2 Circuit element
1. Voltage and current sources.
2. Electrical resistance (Ohm’s law).
3. Construction of a circuit model.
4. Kirchhoff’s laws.
5. Analysis of a circuit containing dependent sources.

2. 2.1 Voltage and current sources
Electrical source : a device that is capable of converting nonelectric energy to electric energy and vice versa.
Ideal voltage source (2.1(a)) : a circuit element that maintains a prescribed voltage across its terminals regardless of the current flowing in those terminals.
Ideal current source (2.1(b)) : a circuit element that maintains a prescribed current through its terminals regardless of the voltage across those terminals.

3. Voltage and current sources
Independent source (2.1) : a voltage or current source in a circuit without relying on voltages or currents elsewhere in the circuit.
Dependent source (controlled source ; 2.2) : a voltage or current source whose value depends on voltages or currents elsewhere in the circuit.
Ideal dependent voltage-controlled voltage source (2.2(a)) :

4. Voltage and current sources
Ideal dependent current-controlled voltage source (2.2(b)) :
Ideal dependent voltage-controlled current source (2.2(c)) :
Ideal dependent current-controlled current source (2.2(d)) :
Active element : a device capable of generating electric energy.
Passive device : a device that cannot generate electric energy.

5. 2.1 (a) : valid; (b) : valid; (c) : not permissible;
(d) : not permissible;
(e) : valid.

6. 2.2
(a) : invalid; (b) : valid; (c) : valid; (d) : invalid.

7. 2.2 Electric resistance (Ohm’s law)
Resistance : the capacity of materials to impede or resist the flow of current.
Resistor (2.5) : a circuit element used to model above behavior.
Ohm’s law (2.6) :

8. Electric resistance (Ohm’s law)
Current as a function of the voltage :
Conductance (siemens (S), mho( )) : the reciprocal of the resistance.
Power at the terminals of a resistor :

9. 2.3

10. 2.3 Construction of a circuit model;
2.9 flashlight circuit
2.10 switch. Short circuit : R=0;
open circuit : R=infinity.

11. 2.5

12. 2.4 Kirchhoff’s laws
Node : a point where two or more circuit elements meet.
2.15 flashlight circuit model Ohm’s law :
Kirchhoff’s current law (KCL) : the algebraic sum of all the currents at any node in a circuit equals zero.
2.15 node KCL :

13. Kirchhoff’s laws
Path : a trace of adjoining basic elements with no elements include more than once.
Closed path (loop) : a path whose last node is the same as the starting node.
Kirchhoff’s voltage law (KVL) : the algebraic sum of all the voltages around any closed path in a circuit equals zero.
2.15 KVL :
The elements are in series when just two elements connect at a single node.

14. 2.16 KCL :
2.17KVL :

15. 2.8
2.19 KCL& KVL.

16. 2.9
2.21(b) for 10ohm :

17. 2.9

18. 2.5 Analysis of a circuit containing dependent sources
1. Once we know , we can calculate using Ohm’s law.
2. Once we know , we also know the current supplied by the
dependent source
3. The current in the 500 V source is .

19. Analysis of a circuit containing dependent sources
2.22 loop KVL :
Node b KCL :

20. 2.10
2.23 Kirchhoff’s law Ohm’s law.
KVL :
Ohm’s law :
Power :

21. 2.11 2.24 transistor amplifier base current KCL :
Dependent source constraint :
KVL :