Download Drawing Circuits

Drawing Circuits
A circuit is a complete electrical path. A complete circuit allows for a
constant flow of electrons and energy output. When drawing circuits,
we use symbols and lines to show the direction of the electrons, as
well as the devices used in the circuit.
Types of Symbols
Symbol Type
Symbol Picture
Connecting Wire: Used to
conduct electricity through a
circuit. Most wires are metal, as
metals are the best conductors.
Drawn simply as line between
different parts of the circuit, it can
either be straight or curved
depending on the circuit.
Cell: Can also be referred to as a
battery or source of the electricity.
One side of the cell or battery is
positive and the other is negative.
OR
The longer line on the cell is
always positive and the smaller is
+ always negative.
Bulb: Light bulbs of different
sizes and brightness can be used
in circuits. The bulb symbol is
connected to the wires with
continuing lines.
Switch: Switches are used to
stop or continue a flow of
electricity. They are simply a
break or completion of the wire
circuit. An example is a light
switch.
- +
Resistor: A resistor restricts the
flow of current. For example, a
dimmer switch on a light switch
can vary the brightness of a bulb
depending on how much
electricity is allowed to flow
through.
Old symbol:
New Symbol:
Ammeter: An ammeter is used to
measure current.
Voltmeter: A voltmeter is used to
measure voltage or potential
difference
Summary statement: These are the basic symbols used in
electrical drawings to show circuits and their parts.
Parts of the Circuit
Create a circuit with a
bulb and a cell.
Create a circuit with a
bulb, cell, and 2
resistors.
Create a circuit with a
cell, a switch, a bulb and
a voltmeter.
Drawing to create
Summary Statement: When drawing circuits, you must have a complete
circuit or loop for your power source to work. If the connecting wire is not brought
back to the original cell, the circuit is not complete and will not work.
Explaining Circuits
Electrical circuits consist of a power source and a load. The
power source can be something like a battery or an outlet.
A load can be something like an appliance or light bulb.
How do Circuits Work?
Electrical circuits are a part of our daily life. In your home,
lamps, televisions, stoves, refrigerators, computers and
many other appliances operate from the same source of
electrical energy. Yet each appliance seems to operate
independently of the others. Does turning on one appliance
affect the current through or the voltage (potential difference)
across, any other appliances? How are the circuits
connected to allow each device to be turned on, while the
others remain off?
Summary Statement:
Circuits are a part of our
daily life and allow us to
use energy. Circuits are
wired to allow us to use
energy in many different
applications.
Types of Circuits
Series Circuits
Series Circuits have only one path for current to flow. Electrons
cannot accumulate, or pile up, at any point in the circuit. All electrons
push the electrons in front of them ahead through the circuit. In a
series circuit, this results in a smooth, even flow of current, because
electrons cannot pile up. Therefore current at any one point on a
series circuit is EXACTLY the same as the current at any other part of
the circuit. The charges making up the current flow from one load,
such as a light bulb, to the next. The charges pass through every load
before returning to the power source to be energized again.
Series Circuits
Race Track Analogy
Race track with several sharp curves.
All cars fill up with gas at one pit stop
and travel around one closed loop.
Every car on the race track follows the
same path.
Draw the Race Track Here:
Series circuits involve ONLY one path
that electrons can travel on. Current is
constant at all points of the circuit. All
electrons are charged at the cell and
travel around the connecting wire.
Parallel Circuits
In a parallel circuit, electrons have many paths to follow. Charges
flow around two or more different loops. After leaving the power
sources, they eventually reach a ‘fork in the road’. Some charges
take one path, while other charges take the other. The current in a
parallel circuit is not the same at different points. Never less, all
charges must go back to the power source to be re-energized, after
traveling around the different branches of the circuit.
Parallel Circuits
City Streets Analogy
Cars have many paths to travel, each
with its own sharp curves or narrow
streets. One path might be a 6 lane
highway, while the other is a 2 lane
side street. Eventually all cars must
return to the service station for more
energy.
Draw the City Street Here:
Parallel circuits involve different or
multiple paths that electrons can
travel on. All electrons must
eventually come back to the cell to
be re-energized. Current is not even
at every part of the circuit.
Parts of the Circuit
Create a SERIES circuit with
one cell, one bulb and one
switch
Drawing to create
Create a PARALLEL circuit
with one cell, two resistors and
one bulb.
Create a PARALLEL circuit
with two cells and two bulbs.
Summary Statement: Circuits in series have constant current and only 1
path. Circuits in parallel have different current at different places in the circuit and
can travel in different paths.
Measuring Voltage, Current and Resistance in Circuits
In electrical circuits, the amount of voltage, current and resistance
can be measured using different equipment.
Picture of Equipment
Description
Voltmeter: A
voltmeter is used to
measure voltage (in
volts) in a circuit.
Voltmeters need to be
placed in a circuit in
parallel and have very
high resistance. If
placed in series, this
high resistance will
cause the circuit to not
work.
Ammeter: An
ammeter is used to
measure current (in
amps) in a circuit.
Ammeters need to be
placed in series such
that the current flows
through the meter. If
placed in parallel the
circuit will short out.
Multimeter: A
Multimeter can be
used to measure
current, voltage or
resistance. Placement
is not an issue as the
device has a larger
capacity.
Bulbs in Circuit: When are they
brighter?
Rules of Thumb
More current = more electrons moving = brighter bulbs
More resistance = less current = less electrons moving = dimmer bulbs
Demo
1 bulb in series circuit
2 bulbs in series circuit
2 bulbs in parallel circuit
3 bulbs in parallel circuit
What happened?