Series/Parallel Circuits
Section 3.1-3.4
Concepts Studied So Far
•
•
•
•
Ohm’s Law: Victory Is Rare
Power: P=IV
KCL
KVL
Outline
• Resistors in Series→ Req
• Resistors in Parallel → Req
• Voltage Divider Circuits →Voltage
divider formula
• Current Divider Circuits →Current
divider formula
Resistors Connected in Series
Series-connected circuit elements car
the same current
Equivalent Resistor
Req=R1+R2+R3…
Exercise
Identify the resistors connected in seri
Resistors in Parallel
• Parallel-connected circuit elements
have the same voltage across their
terminals
Equivalent Parallel Resistor
1/Req=1/R1+1/R2+1/R3+1/R4
Series Parallel Simplification
P3.5
Find Rab
P3.7
Find Rab
The Voltage-Divider Circuit
Function: to develop more than one v
level from a single voltage supply
A Voltage Divider Connected to
a Load
The Current Divider Circuit
Example 3.3
Calculate power dissipated in the
6 Ohm resistor
Problem 3.14
vo(no load)=4 V
vo(load)=3 V
Find RL
3.15
Assume that only 0.5 W resistors are available
The no-load voltage is to be the same as in the schematic.
Specify the smallest values of R1 and R2
Application: Photovoltaic
System
• Solar Cell
– I-V Characteristics Equation
– Series construction
– Parallel construction
I-V Characteristics of a Solar Cell
Short Circuit
Current I(Isc)
Open Circuit Voltage (Voc)
I-V Characteristics shows all the possible operating point
for the solar panel
Open Circuit Voltage
Measurement
Observation: there is no current at Voc.
Short Circuit Current
Measurement
Why is OK to short circuit a solar
cell?
It is possible to produce short circuit a solar panel because
The current comes from the electrons produced by the
solar cell. Only some of the photons striking the solar cell
are converted into current. The current produced by
the solar cell is finite.
Power Produced by Solar Cell
P=IV
Observation: No power is produced at
Voc and Isc. Why?
Example
If Vmp is 15 V and Imp is 3A, what resistance is required
in order to operate the solar cell at its maximum power?
Answer: A 5 Ohm load.
Rule of Thumb
• Solar cells are generally connected in
series to achieve a desired voltage.
• The serial connected solar cells are
connected in parallel to build current
and power.
• Cells are connected to form modules
and modules are connected to form
array.
Connect Cells/Modules in Series
Individual cells are connected in series by soldering the metal strip
from top surface (- terminal) of one cell to the back surface (+ terminal)
of the next
Use Series Connection to
Increase Voltage
You want to use cells of matching current capacity!
Use Parallel Construction to
Increase Current
(Acquire proper voltage)
Increase Current Capacity
by Connecting Cells in Paralell