Download Science 9 Unit 4: Electricity Name:

Science 9
Unit 4: Electricity
Name:
Topic 2 - Electricity within a Circuit
A circuit is a pathway that allows the flow of electricity. Most electrical circuits use
wires (as conductors), although others may use gases, other fluids or materials.
All circuit diagrams have four basic parts:
1. source - provides energy and a supply of electrons for the circuit
(ex. Battery)
2. conductor - provides a path for the current (Wires)
3. switching mechanism - controls the current flow, turning it off and
or directing it to different parts of the circuit Switch
on,
4. load - converts electrical energy into another form of energy (ex. Bulb,
motor, toaster)
Basic Circuit Symbols
A drawing made with these symbols is called a schematic or schematic diagram.
The rules to follow when making schematic diagrams:
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Use a pencil and ruler on graph or unlined paper
Place the components in a rectangular or square arrangement
Conducting lines should be straight with ‘right-angled’ corners
Do not cross conductors
Be neat and make the sizes of the symbols consistent and easy to see
Measuring Current
Current (I)-The steady flow of charged particles. The flow continues until the
energy source is used up, or disconnected.
Amperes (A)- The rate at which an electrical current flows (measurement for
current).
Galvanometer (mA)- An instrument used to measure very weak electric current
Ammeter – used to measure larger currents.
Measuring Voltage
Electrical energy is the energy carried by charged particles. Voltage is a measure
of how much electrical energy each charged particle carries. The higher the
energy of each charged particle, the greater the potential energy. Also called
'potential difference', the energy delivered by a flow of charged particles is equal
to the voltage times the number of particles. Voltage units are volts
(V), and for safety purposes, the voltage of most everyday devices we commonly
use is relatively low, while industries and transmission lines are relatively high.
Voltmeter - used to measure voltage [red to positive (+) and black to negative (-)]
Some voltmeters can measure a wide range of voltages. These multi-meters
should be used with caution, so that the sensitive needle is not damaged (by
testing a low range with high voltage).
Rivers of Electricity
Electric circuits are often compared to water systems. Electric charge is like the
water, as it flows (input) it makes changes in the energy that results (output).
A model for:
VOLTAGE
Waterfalls
 A) Niagara Falls would simulate a large flow of current and a very large
potential difference (ie 100 V)
 B) A small waterfall at 10 M in height and many rocks slowing the water
would have a potential difference of (10 V) but it would have less of a current
because the rocks create resistance.
 C) A similarly small waterfall of 10 M would have the same potential
difference of 100 V, but it may not have any rocks slowing the flow and
therefore it would have a higher current than the 2nd waterfall.
CURRENT
 The longer and thinner the wire is the more resistance the electrons face and
the less current there will be. A shorter wider wire will provide the path of
least resistance and more current will pass.
Topic 2 Assignment
Vocabulary:
Circuit
Something that helps the transfer of
electricity
Source
A source of electricity to begin
Conductor
Something that allows electrons to flow
through easily
Load
Something such as a light bulb that takes
the electricity
Switch
Something that can block or allow
through the electricity
Current
The flow of electrons
Ampere
Rate at which an electrical current flows
at
Voltage
Amount of electrons the power source
has
Potential difference
Potential amount of energy released
through a power source
Voltmeter
A meter that measures voltage
Ammeter
Used to measure large currents
Galvanometer
Used to measure weak electrical currents
The thing that uses the electricity
Assignment:
1. Complete the Topic 2 Review questions on page. 278 #1-5
1. A-4, B-5, C-6, D-2, E-1, F-3
2.
3. You would connect to the wires that are conducting the electrical currents
4. I would say that the electric iron because it is made of iron which is a metal which
is a very good conductor of electricity
5. 12V
2. Complete the table
(You may have to do a little digging to find these!!!)
Making Light Bulbs Glow
What to Do
In each of the eight diagrams below, the electric light will not work. Use the space provided to
explain what is wrong with each arrangement, then adjust each diagram so that the light will work.
Diagrams