Download How Series and Parallel Circuits Differ

13.10
HOW SERIES AND PARALLEL
CIRCUITS DIFFER
Review
Current

Current is the rate of charge flow and is
given the symbol I. Current is the total
amount of charge moving past a particular
point in a conductor divided by the time
taken.
Measurement of current

An Ammeter (a current measuring
device) must be wired so that all current
flows through it. The ammeter must be an
excellent conductor so that no energy is
lost due to its addition to the circuit.
Current

Charge

Time
SERIES AND PARALLEL
CIRCUITS
Series Circuits
 An electric circuit in which
the components are
arranged one after
another in series.
 A series circuit has only
one path along which
electrons can flow.
 If that pathway is
interrupted, the whole
circuit cannot function.
Series Circuits
 The amount of current is the same in all parts
of a series circuit.
 If more resistors are added, it will increase the
total resistance of the circuit.
 This decreases the current.
Series Circuits
 Example: Adding an extra bulb to a series
string of lights makes all the bulbs dimmer.
 Electrons use up all their potential difference
going around a series circuit no matter how
many loads are in the circuit. Each load will
use part of the total potential difference,
depending on how much it resists the flow of
electrons.
Current Through Loads in Series
 If you have a circuit with one load (fig 1 A), the total resistance of the
circuit will be different than if you have two or more of those loads
connected in series (fig 1 B).
 The electrons have only one path to follow and with two or more
loads, they have more “bumps” to deal with along the way.
 Therefore, the current flowing through the
circuit in (fig 1 B) will be less than the current
flowing through the circuit in (fig 1 A)
Voltage across Loads in Series
Parallel Circuits
 A parallel circuit is an electric circuit
in which the parts are arranged so
that electrons can flow along more
than one path.
 The points where a circuit divides
into different paths or where paths
combine are called junction points
 An interruption or break in one
pathway does not affect the other
pathways in the circuit.
Parallel Circuits
 Similarly, adding a new pathway with more
resistors does not affect the resistance in any
of the other pathways.
Current through Loads in Parallel
Current through Loads in Parallel
Parallel Circuits
 Each electron has the same amount of
energy, and electrons must expend all their
energy on the path they are on.
 This is why the potential difference across
parallel resistors will always be the same,
even though the resistors themselves are of
different values
Voltage across Loads in Parallel
Summary of Differences
Summary of Current, potential
difference, and resistance in
series and parallel circuits.
Circuit
Potential Difference
Series
circuit
Each load uses a portion of the
total potential differences
supplies by the battery
VT = V1 + V2 + V3
Summary of Current, potential
difference, and resistance in
series and parallel circuits.
Circuit
Potential Difference
Parallel
circuit
Each load uses all the
potential difference supplied
by the battery.
VT = V1 = V2 = V3
Summary of Current, potential
difference, and resistance in
series and parallel circuits.
Circuit
Current
Series
circuit
The current is the same
throughout a series circuit
Itotal = I1 = I2 = I3
Current in a series circuit example
 IT = I1 = I2
 I3 = 10 A
10.0 A
= I3
30 V
10.0 A
10.0 A
R1
30 V
I3
V2
100v
R2
Summary of Current, potential
difference, and resistance in
series and parallel circuits.
Circuit
Current
Parallel
circuit
The current divides into different
paths. A pathway with less
resistance will have a greater
current
Itotal = I1 + I2 + I3
Current in a parallel circuit example
 IT = I1
 I3 = I T
= 3A
9.0 A
30V
30V
R3
V2
R2
30V

+ I2 + I3 = 9 A
– I1 – I2 = 9 A – 3 A – 3A
R1
3.0 A
3.0 A
I3
Two Types of Circuits Combined
 Some circuits are combinations of series
circuits and parallel circuits. These
combinations help prevent problems such as
the all the lights in the house going out
because one bulb burnt out.
 It is also an important safety feature in a
combination circuit to have some switches
wired in series, because it is sometimes
necessary to turn off the electricity in part or
all of a home
HOMEWORK
 Page 575 # 2-7