EGR 101 11

Example Series Circuit

• What is the total resistance?

• What is the current, IT?

• What is the voltage across each resistor?

V1

V2

EGR 101 22

Kirchhoff’s Voltage Law Note, in the example on the

previous page,Vs = V1 +V2

EGR 101 33

Series Circuit Characteristics Series circuits have the following

voltage characteristic:

nS VVVV ...21

whereVS = the source (or total supply) voltageVn = the voltage across the highest numbered

resistor in the circuit

EGR 101 44

Voltage Relationships

Kirchhoff’s Voltage Law The sum of the component voltages in a

series circuit must equal the net source voltage

1840 – German Physicist, Gustav Kirchhoff

nS VVVV ...21

EGR 101 55

Series Circuit Characteristics Power Characteristics

...21 TnSSS PPPPIVP

wherePS = the source powerPT = the total power dissipated by the circuitPn = the power that is dissipated across the

highest numbered resistor in the circuit

EGR 101 66

Team Activity # 1: Refer to Figure 4.45(d) on p. 125 of textbook

Method 1: Calculate the total resistance of the circuit, RT.

Calculate I using RT and Ohm’s Law.

Calculate the total power PT using Vs and I.

Method 2: Calculate I using Ohm’s Law. Calculate the voltage across each resistance, V1, V2,V3 &

V4.

Calculate the power in each resistor P1, P2, P3 & P4.

EGR 101 77

Comparison of Results Questions:

Does the VT you computed in Method 2 equal Vs from Method 1?

Does the sum of P1, P2, P3 & P4 equal PT from Method 1?

EGR 101 88

Single subscript, VA – indicates the voltage is measured from the specified point relative to ground

Two subscripts, VAB – indicates the voltage is measured from the first identified point to the second

Voltage Notations

A

} VA

} VAB

A

B

} V?

+

_

+

_

+

_

EGR 101 99

Voltage Divider The Voltage Divider Relationship

– Often used to analyze a portion of a series circuit

Allows us to determine individual voltages

R11k

R21k

R31k

Restof

Circuit

A

B

}}

}

V1

V2

V3

EGR 101 1010

Voltage Divider Relation For a series combination of N resistors with

Vs (VAB in previous slide) applied across them, the voltage across Rn is:

whereRn = the resistor n of interestVn = the voltage across across Rn

RT = the total series resistance

T

nsn R

RVV

EGR 101 1111

Team Activity # 2: Refer to Figure 4.46(c) on p. 125 of textbook

1. Calculate the voltage across each resistor, R1, R2, & R3 by the Voltage Divider Method.

2. What is the resistance from point A to ground?

3. Calculate the current through each resistor using your results from step 1.

4. Calculate the current in the circuit based on Vs and total resistance.

5. Do your results from steps 3 and 4 agree?

EGR 101 1212

Audio Amplifier Application

?BV

The Potentiometer as a Voltage Divider

EGR 101 1313

Team Activity # 3: Refer to Figure 4.39(b) on p. 122 of textbook

Solve problem 12.