1. ECE 1270: Introduction to Electric Circuits
Lecture 2:
Ohm's Law
Chapter 2
Circuit Elements

2. Voltage and Current Sources
An Ideal
Voltage Source
An Ideal
Current Source
An ideal voltage
source will provide a constant voltage across its terminals regardless of the current flowing into those terminals
An ideal current source will provide a constant current flowing through its terminals regardless of the voltage across those terminals

3. Voltage and Current Sources
____ Controlled Voltage Source
____ Controlled Voltage Source
____ Controlled
Current Source
____ Controlled Current Source

4. Example 2.1: Valid or Invalid?
(b)
(a)
Valid: a,b,e, Invalid: c,d
(c)
(e)
(d)

5. Example 2.2: Valid or Invalid?
(c)
Valid: b,c Invalid: a,d
(b)
(d)

6. AP 2.1

7. Ohm's Law R =Electrical Resistance [Ω] v = Voltage [V] i = Current [A]
Resistance is created by the atoms in a material through which the electrons are moving

8. Example 2.4: Circuit Model of a Flashlight
Lamp
Coil Wire
Metal Case
Switch

9. P2.9, P2.11