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
1
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.
EGR 101
2
Today’s Agenda
Chapter 4
Series Circuits
Voltage Divider
3
Series Circuit
Circuit – a circuit that
contains only one current path
 Series
EGR 101
4
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
5
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
B
C
D
E
F
EGR 101
6
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?
R2
22kOhm
R1
22kOhm
XMM1

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?
EGR 101
7
Series Connection
Characteristics
 Total
Series Resistance
RT  R1  R2  ...  Rn
where
RT = the total series resistance
Rn = the highest-numbered resistor in
series
EGR 101
8
Example Series Circuit
V1
V2
•What is the total resistance?
•What is the current, IT?
•What is the voltage across each resistor?
EGR 101
9
Kirchhoff’s Voltage Law

Note, in the example on the
previous page,
Vs = V1 +V2
EGR 101
10
Series Circuit Characteristics

Series circuits have the following
voltage characteristic:
VS  V1  V2  ...  Vn
where
VS = the source (or total supply) voltage
Vn = the voltage across the highest numbered
resistor in the circuit
EGR 101
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Voltage Relationships

Kirchhoff’s Voltage Law

The sum of the component voltages in a
series circuit must equal the net source
voltage
VS  V1  V2 ...  Vn

1840 – German Physicist, Gustav Kirchhoff
EGR 101
12
Series Circuit Characteristics

Power Characteristics
PS  VS I S  P1  P2  ...  Pn  PT
where
PS = the source power
PT = the total power dissipated by the circuit
Pn = the power that is dissipated across the
highest numbered resistor in the
circuit
EGR 101
13
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
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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
15
Voltage Notations


Single subscript, VA
– indicates the voltage
is measured from the
specified point relative
to ground
A
+
_
+
Two subscripts, VAB
– indicates the voltage
is measured from the
first identified point to
the second
A
_
+ B
_
EGR 101
}
VA
}
}
VAB
V?
16
Voltage Divider

The Voltage Divider Relationship
– Often used to analyze a portion of a
series circuit
A

Allows us to
determine
individual
voltages
R1
1k
Rest
of
Circuit
R2
1k
R3
1k
B
EGR 101
}
}
}
V1
V2
V3
17
Voltage Divider Relation

For a series combination of N resistors with
Vs (VAB in previous slide) applied across
them, the voltage across Rn is:
Rn
Vn  Vs
RT
where
Rn = the resistor n of interest
Vn = the voltage across across Rn
RT = the total series resistance
EGR 101
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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
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The Potentiometer as a
Voltage Divider

Audio Amplifier Application
VB  ?
EGR 101
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Team Activity # 3: Refer to Figure
4.39(b) on p. 122 of textbook

Solve problem 12.
EGR 101
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