Download Grade 9 Applied Science – Electricity

Grade 9 Applied Science – Electricity
Drawing, Reading and Building Electrical Circuits
Drawing, reading and building electrical circuits is an important skill…especially for electrical engineers,
electricians, building contractors and scientists.
There are two types of circuits: (1) series and (2) parallel. As shown in the diagram below, a series
circuit is one single path; whereas, a parallel circuit has numerous paths.
In the following table, list other features of each type of circuit that you have observed from building some
circuits in class.
Table 1. Features of Series and Parallel Electrical Circuits
Feature
Series Circuit
If one light bulb is removed
All lights in the circuit go out
Parallel Circuit
All other bulbs still work
Brightness of bulb as more bulbs
are added to the circuit
Voltage in circuit as more bulbs
are added to the circuit
Electrical Symbols
Table 2. Some Common Electrical Symbols
Using the correct electrical symbol is
important….otherwise, you might build
the wrong thing.
NOTES
 A Voltmeter measure the
potential difference or voltage
drop across a load in a line (e.g.,
light, resistor, bell, motor). As
such, the Voltmeter is always
drawn and installed PARALLEL
to the load being measured
 An Ammeter measures current.
The Ammeter is drawn and
installed in the circuit (SERIES)
 The flow of electrons in an
electrical circuit is from the NEGATIVE terminal to the POSITIVE terminal of the
power source (e.g., battery). In the symbol for a battery, the smaller line is the
negative terminal. A symbol for a two-celled battery highlighting the different
terminal charge positions is shown.
Task

On separate pieces of paper, draw the following electrical circuits
1. A circuit with a three-cell battery and two lights. The two lights are in a parallel circuit.
One switch turns both lights on and off.
2. A circuit with a two-cell battery with three lights. Two lights are in a series circuit while
the other light runs in a circuit parallel to the other two lights. A switch is added that
controls the lights in the series circuit. A voltmeter measures the voltage drop across the
light in the parallel circuit.
3. A circuit with a four-cell battery and four lights, one electrical motor and one resistor
(Resistance unknown). Three lights are wired in a series circuit. The fourth light is wired
in a circuit parallel to the other three lights. The parallel circuit also has a motor that is
wired in series to the fourth light. Another parallel circuit has the resistor. A voltmeter is
wired to the resistor circuit to measure the potential difference across the resistor. A
switch controls the three lights in series and another switch controls the light and motor.

Using the circuit boards and other equipment, build Circuit 1 and Circuit 2 using your electrical
drawing. Review your circuits with the teacher.

Exchange your Circuit 3 drawing with a neighbor and build Circuit 3 according to the drawing of
your neighbor.

Compare your Circuit 3 with your neighbour’s circuit. Do they work? Are they similar? What
differences, if any, exist? If so, who is right?