EGR 101 11

Retention Assessment Put your books away and take out a

sheet of paper. Answer the questions below to the best of your ability.

When you have finished, fold your paper in half and raise your hand to have your paper collected.

Your score will count toward In-Class activities

EGR 101 22

Quiz 1. What is the relationship between current

and charge?

2. Express voltage in terms of charge, energy, and/or time.

3. Express Power in terms of charge, energy, and/or time.

4. State Ohm’s Law.

33

Today’s AgendaChapter 4

Series CircuitsVoltage Divider

EGR 101 44

Series Circuit Series Circuit – a circuit that contains

only one current path

EGR 101 55

Series Circuit Characteristics Current Characteristics – the current through any element in a series circuit

must equal the current through every other element in the circuit

EGR 101 66

Series Connections Two elements are connected in series if

ALL of the current of one element flows through the second.

Which of the following are in series?A CB

F

D E

EGR 101 77

Relation to Lab Activity In the lab last week, for one of

the circuits, you had 2 resistors connected as shown to the right (with different values) and a meter set on Ohms measuring them. Are the resistors in series?

What resistance would the multimeter read if you built this circuit?

What would the meter read if you put 10 22k-Ohm resistors in series?

R122kOhm

R222kOhm

XMM1

EGR 101 88

Series Connection Characteristics

Total Series ResistancenT RRRR ...21

whereRT = the total series resistanceRn = the highest-numbered resistor in

series

EGR 101 99

Example Series Circuit

•What is the total resistance?

•What is the current, IT?

•What is the voltage across each resistor?

V1

V2

EGR 101 1010

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

previous page,Vs = V1 +V2

EGR 101 1111

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 1212

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 1313

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 1414

Team Activity # 1: Refer to Figure 4.45(d) on p. 125 of textbookMethod 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 1515

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 1616

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 NotationsA

} VA

} VAB

A

B } V?

+

_

+

_

+

_

EGR 101 1717

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 1818

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 RRVV

EGR 101 1919

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 2020

Audio Amplifier Application

?BV

The Potentiometer as a Voltage Divider

EGR 101 2121

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

Solve problem 12.