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Analyzing & Building
Electrical Circuits
Learner Outcomes:
 Predict the effects of switches, resistors and other
circuit diagram symbols.
 Draw circuit diagrams for toys, models, and
household appliances.
 Compare and contrast micro-electronic circuits and in
a house.
Shrinking Circuits
The most economical way…
To connect all the components
in a circuit is in a simple loop.
What could be a problem with a
simple loop?
Circuit Drawings
Engineers & designers use
schematic diagrams.
Special Symbols
 That show the components and
connections clearly.
 These symbols make it easier to
plan and analyze a circuit before
you build it.
Parts of a Circuit
All circuits have 4 basic parts:
Sources
Conductors
Switching Mechanisms
Loads
Source
 Provides energy and a supply of electrons
for the circuit.
Conductor
 Provides a path for current. Wires are
drawn as straight lines in a schematic
diagram.
Switching Mechanism
 Controls the current flow- turns it on and off,
or directs it into different parts of the circuit.
Load
 A load converts electrical energy into some
other form of energy.
Series Circuit
Parallel Circuit
Combination Circuit
Comparison
Series Circuit
Parallel Circuit
 If pathway is interrupted, the
whole circuit cannot function.
 Adding components increases
the total resistance of the
circuit. This means that adding
an extra bulb to a string of
lights makes all of the bulbs
dimmer.
 Interruption or break in one
pathway does not affect the
rest of the pathways in the
circuit.
 Adding a new pathway does
not affect resistance in other
pathways- in fact, adding extra
resistors decreases the total
resistance of the circuit.
Adding more paths for the current means
less total resistance.
Series Circuits
 Do have an important use- in houses for
example, switches are wired in a series
with other components (wall plugs,
lights) which makes it possible to turn
off all the electricity in the circuit.
 You must use a series circuit for
switches.
However…
 Household wiring is one of the
many applications that use parallel
circuits.
 You wouldn’t want your
refrigerator to go off if a bulb
burned out, would you?
 A switch in one branch of a parallel circuit only
controls the devices in that branch.
 A switch in a series with all the branches
controls all of them.
Microcircuits
 Regular switches are practical and convenient
for your home, but what is used in tiny circuits
like those used in advanced electronics?
Transistors
 Solid State- made of solid material with no
moving parts.
 Most are made with 3 layers of specially
treated silicon.
 A small voltage through the middle layer
controls a current between the outer layers
(in this way transistors can act as switches).
Microcircuits (Integrated Circuits)
 Are made up of microscopic transistors and resistors.
 They are circuits on extremely small scales.
 The latest microcircuits contain more than a million
components in a square centimetre.
Check & Reflect
 Page 316, 1-11
 Due Monday, March 21 , 2015