Download Electricity - PawPrints212

Learning Targets: To work with electronic components and meters to build
circuits, measure and monitor electric properties, and explain the
interactions taking place in the systems.
 Humans have been
aware of this force for
many centuries.
 Ancient man believed
that electricity was
some form of magic
because they did not
understand it.
Today we know of only
4 forces:
electromagnetism
 Strong nuclear force
 Weak nuclear force
 Gravity

About 3,000 years ago, a Greek
philosopher named Thales
(Θαλής) noticed that when a
piece of amber was rubbed
with wool cloth, it would
attract lightweight objects such
as straw or feathers.
Amber is a yellow-orange rock
made of fossilized tree resin
(similar to sap).
The Greek name for amber is
‘elektron’, and is the origin of
our word electricity.
Static
Lightning
AnBf
Bioelectricity (Electric Eel)
Animal/Human Nervous Systems

Wall outlets (dangerous)

Batteries (safe for classroom experiments)

Generators/Coal & NuclearPowerplants

Solar Cells

Wind turbines

Hydroelectric plants
Electricity is a naturally occurring form of
energy.
It is a force that exists all around us.
Static electricity is
Current electricity is a movement of charge,
and in most cases the particle carrying the
charge is the electron.
Can be used to do work.
Can be converted into other useful forms of
energy including:
 Light
 Sound
 Heat
 Motion
Students will:
Discover how to create complete circuits and how to identify series, parallel, and short
circuits.
Demonstrate that closed circuits allow current to flow and open circuits do not allow
current to flow.
Create and compare intensity of light produced by lamps in series and parallel circuits.
Observe that a switch can turn a lamp on and off by completing a circuit or creating a
short circuit.
Set up circuits described in schematic diagrams.
Demonstrate the different performance of lamps in series and in parallel.
Describe how short circuits create an electric pathway that bypasses the intended
components.
Communicate circuit designs and components using a symbolic system called
schematic diagrams.
Is the study of the effects of electrons moving
through a vacuum, a gas, or a material.
Putting obstacles in the path of a stream of
electrons to see if we can make them do
something interesting or useful.
Smoke alarms
Portable radios
To change electric energy into light, using a
9-V battery and an electric component called
a lamp.
Work with one partner – your team will be
given a number.
One set of materials to share: 9-V battery
with wires (leads), and one light bulb (lamp)
5 minutes
Electricity from the battery can make the
lamps produce light.
Electricity had to go in an unbroken pathway
from one side of the battery, to the lamp and
back to the other side of the battery.
The two connectors on the battery are called
terminals, the positive terminal and the
negative terminal.
Electricity flows in a pathway called a circuit.
If the circuit is closed, or complete, all the
way from one terminal to the other, the
electricity will flow and the lamp will glow.
If the circuit is open (broken) someplace, the
electricity will not be able to flow, and the
lamp will not glow.
The flow of electricity is called current.
Electric current is due to the movement of
electricity, rather like a river current is due to
the movement of water.
The current that flows from a 9-V battery is
called direct current.
Direct current flows in one direction only
through the circuit.
Current flows from the negative terminal to
the positive terminal of the battery.
The red wire (hot wire) is connected to the
positive and the black wire is connected to
the negative terminal.
 Each team will have its own set of components.
You will
keep them in a bag. You will be the only students to use
your components, so keep track of them carefully.
 Your bag will have your team’s number written on it. You
will use only the bag of components with your team’s
number. The component bags will be kept in the file.
 At the beginning of each class, you will come here to get
your components, and at the tend of each class you will
inventory our components and put them away in the same
place.
 Right now you will have one lamp in your component
bags, but soon you may have a dozen or more items.
 Batteries will be shared with other class. These will not be
kept in the component bags.
GOAL
Students will:
Explore, measure, and manipulate one of the two main attributes of
electricity (voltage) and discover how voltage can be influenced by
components in a circuit.
OBJECTIVES
Measure voltage drops using a digital voltmeter.
Conduct systematic investigations of resistors and lamps to discover how
components affect voltage.
Discover that the sum of the voltage drops across the components in a series
circuit equals the voltage at the source.
Calculate the percentage of voltage drop and percentage of resistance imposed
by components in series circuits.
Explain voltage as a push that moves current through a circuit.
Explain the relationship between voltage drops and resistances of the
components in a circuit.
Describe dynamics in terms of the three great truths of circuitry.
Explain that resistance imposed by a component and voltage drop across that
component are proportional.
Measuring Voltage
We have been finding out some things about
electricity and what it does when it moves
through circuits containing various components.
Today we will start an investigation to find out
what moves electricity through the circuit.
Electricity is a flow of electrons.
The flow of
electrons is called current.
Electrons move when a force is applied to
them.
The force moving the electrons is called
voltage.
When you hear someone mention the
voltage of an electricity source, they are
talking about the amount of push available to
move current through a circuit.
See CD ROM – Explanation of Voltage in the
Technical Manual, Voltage and Batteries
section.
 The same meter used to measure resistance can be
used to measure voltage.
 Project the transparency called Voltmeter and
introduce it.
 Turn the rotary switch 3 clicks counterclockwise to the
20-V setting.
 At this setting, the voltmeter can measure voltage
between 0 and 20 V.
 Voltage is ALWAYS measured with the current flowing
through the circuit.
 Do NOT move the switch on the meter to measure
resistance while you are working with electrified
circuits.
The difference in the amount of voltage on
the two sides of a component is what the
voltmeter measures.
The voltmeter measures the amount of
voltage “used” by a component.
The amount of voltage used by a component
is its voltage drop.
We will always refer to the voltmeter reading
as a voltage drop.
Use your meters and other components,
including the springboards and batteries to
explore voltage.
How much voltage drop is available across
the poles of your battery?
What is the voltage drop across a lamp
connected directly to a battery?
When the lamp is in a series with a 75-Ω
resistor?
With a 330- Ω resistor?
What is the voltage drop across one, two, and
three lamps? Compare the voltage reading of
each lamp when they are in series and when
they are in parallel.
10 min. free exploration
See the transparency called “Measuring Voltage Drops
in 4 Circuits”.
 Demonstrate:
 Draw a schematic of the first circuit. This one had two 150-
Ω resistors.
 Measure the voltage drop across a component.
 Write the voltage drop in a circle near the component
symbol on the schematic.
 Draw two lines from the sides of the circuit to the
schematic showing where you placed the two probes, or
simply write the voltage on a short line next to the
component.
See Lab Notebook p. 11
1. Find the components required.
2. Set up the circuits.
3. Measure the voltage drops in each circuit.
4. Record your measurements on the schematics
of the circuits.
Report what you found out about voltage drops in
your circuits.
 The battery drops _____ volts.
 The battery has the highest voltage drop.
 The resistor has the second highest voltage
drop.
 The resistor doesn’t always drop the same
amount of voltage.
 The lamp drops more voltage when it is bright.
 The switch doesn’t drop any voltage when it is
closed, but it drops a lot of voltage when it is
open.
 Voltage is what moves current through circuits.
 Voltage is like a force – a push or a pull.
 When the electricity is pushed through some
components, like resistors and lamps, the
amount of available push is reduced. We can
measure how much the available push is
reduced with a voltmeter.
 The difference in the amount of voltage on the
two sides of a component is what the voltmeter
measures.
 We call that reduction of voltage a voltage drop.
Which components had the largest voltage
drops? (battery & resistor)
Which components had the smallest voltage
drop? (lamps)
Hand in the “Measuring Voltage Drops in Four
Circuits” sheet.
Return the components to your bags
Secure the battery leads.
Turn the multi-meter off.
Return all materials to the materials station.
The Resistance / Voltage Relationship
Think – Write – Pair – Share:
How do you explain the voltage drop across
the lamp in a circuit. (4 min)
Open your Lab Notebook to Resistor
Investigation from Inv. 2.
 Review: The greater the resistance in series with a
lamp, the dimmer the lamp glows.
Lab Notebook p. 12
 Repeat the series of investigations with the
resistors of various values
▪
▪
▪
▪
75 Ω
150 Ω
330 Ω
1000 Ω
But this time, measure the voltage drops across the
lamp and the resistor in each circuit.
Add one additional resistor to your
investigation: The resistor is
black/black/black, or a theoretical resistor of
0Ω
How could you make a resistor with 0 of
resistance?
 Use the copper wire from your component bag!
Get springboards, component bags, multi-
meters. (15-20 min)
Resistor Resista
Code
nce
(ohms)
Lamp
Brightness
bl/bl/bl
0
Very bright
v/gr/bl
75
Bright
br/gr/br
150
Medium
or/or/br
330
Dim
br/bl/r
1000
No light
3 Groups report the
values for lamp
voltage drop. (Use the
median in the next
column)
Lamp
Voltage
Drop
Resistor
Voltage
Drop
Is there a pattern in the amount of voltage drop across the resistors?
•The greater the resistance, the greater the voltage drop across the resistor.
Is there a pattern in the amount of voltage drop across the lamp?
•The greater the resistance, the less the voltage drop across the lamp.
How do these voltage-drop patterns relate to the size of the resistor in the circuit with the lamp?
•As resistance increases, the voltage across the resistor increases, and the voltage across the lamp decreases.
Add up the lamp and resistor voltages for each resistor. Is there a pattern?
•The sum of the voltage drops in the circuit equals the available voltage across the terminals of the battery.
Hand in the “Resistor/Voltage Investigation”
sheet.
Return the components to your bags
Secure the battery leads.
Turn the multi-meter off.
Return all materials to the materials station.