Chapter 4. Circuit Theorems

Question 1

What is the superposition principle?

Answer 1

we apply one INDEPENDENT source at a time.
1. we turn off all independent sources except one source. then use any of the other methods to solve for current or voltage output
2. Repeat for all other independent sources
3. Then add all the contributions due to the independent sources

Question 2

What is source transformation?

Answer 2

It is possible to transform a source from one form to another

Question 3

What can we replace a voltage source (independent or dependent) in series with a resistor with?

Answer 3

It can be replaced by a current source (independent or dependent) in parallel with a resistor

Question 4

If you replace a voltage source with a current source, which way should the arrow be pointing?

Answer 4

The arrow should be pointing toward the positive terminal

Question 5

What is linearity?

Answer 5

• linearity in a circuit means that as current is changed, voltage is changed proportionally
• also the response of a circuit to a sum of sources will be the sum of the individual responses

Question 6

What does Thevenin’s Theorem state?
What does the new voltage and resistor equal?

Answer 6

it states that a linear two terminal circuit may be replaced with a voltage source and resistor in series.

voltage source = open circuit voltage at the terminals

resistance = resistance measured at the terminals when all independent sources are turned off

Question 7

What are the two cases of Thevenin’s Theorem?

Answer 7

1. If there are no dependent sources, then the resistance may be found by simply turning off ALL the sources
2. If there are dependent sources, turn off all independent sources. Then apply a voltage or terminal to the terminals and determine the corresponding current )or voltage)

Question 8

What does a negative resistance mean

Answer 8

it implies that the element is supplying power

Question 9

What does Norton’s Theorem state?

Answer 9

states that a linear terminal circuit may be replaced with an equivalent circuit containing a resistor + current source

Norton resistance will be exactly as Thevenin

Question 10

How do we find norton’s current?

Answer 10

found by short circuiting the circuit’s terminals and measuring the resulting current

Question 11

assuming the load resistance can be varied, how do we find the maximum power? (equation)

Answer 11

p = [Vth/(Rth + RL)]² * RL