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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.