Lecture 4

• Complex impedance • Thevenin and Norton • bode plots • decibels

What’s the impedance of a short piece of thick wire?

A) Very large and mostly real B) Very large and mostly complex C) Very large but can be complex and/or real D) About zero E) Can’t tell with the given information

What is inside the power supply?

A)Lots of wire B) An ideal voltage source and some R C) An ideal current source and some R D)A complex circuit to understand… E) No idea

What is inside the power supply?

Answer: A complex circuit to understand…

That can be modeled as an ideal voltage source and some R

OR, as an ideal current source and some R

For any combination of simple voltages and linear resistors, you can find an equivalent circuit composed of a single voltage source and a single equivalent resistor, that will produce the same current (and voltage) through RL. (AND Vth and Rth are independent. of RL.)

To measure the current thru resistor 3, how should the ammeter be attached?

e) MORE than one of these choices is ok.

12 V

A

A

A

A

a)

b)

c)

d) 1

2

3

4

B5

B6

An ideal ammeter should have

A) Zero resistance

B) Infinite resistance

C) A well defined resistance > 0 (e.g. 1 or 1k)

D) Shiny red color

To measure the voltage across resistor 3, how should the voltmeter be attached (assume you only attach one at a time)?

e) MORE than one of these choices is ok.

12 V

V

V

V

V

a)

b)

c)

d) 1

2

3

4

B7

B8

An ideal voltmeter should have

A) Zero resistance

B) Infinite resistance

C) A well defined resistance >0 (e.g. 1 or 1k)

D) Shiny red color

What’s the magnitude (i.e. ‘modulus’) of the impedance of a good voltmeter?

A) Very large B) Very small C) Doesn’t matter. Could be either, large or small.

What’s the magnitude (i.e. ‘modulus’) of the impedance of a good ammeter?

A) Very large B) Very small C) Doesn’t matter. Could be either.

What’s the magnitude (i.e. ‘modulus’) of the impedance of a good voltage source?

A) Very large B) Very small C) Doesn’t matter. Could be either.