Download Explore: How does electricity work? Supplies: Batteries of different

Explore: How does electricity work?
Supplies:
Batteries of different sizes (AA,AAA,C,D)
Wire or copper tape (http://www.digikey.com/product-search/en?lang=en&site=us&KeyWords=3M1181A-ND&x=11&y=11)
Various light bulbs (make sure they can handle power from the batteries)
3X5 index Cards (If using copper tape)
Computer to go to PhET Circuit Construction Kit Simulation (DC only)
(http://phet.colorado.edu/en/simulation/circuit-construction-kit-dc)’
Give students batteries, wires/copper tape, and light bulbs, and 3X5 cards (if using copper tape)
and have them light up a light bulb and explore what else they can make with it. Can they light up more
the one bulb at a time? Are the bulbs dim or bright? Have them explain the set up? If comfortable with
them throw in some resistors and have them explore them too.
Have students keep notes on what they did and why, and what they observed when they did it.
This will start to get them familiar with the way electricity works and how to connect light bulbs. Have
students develop a bubble map of their thinking with electricity in the middle and making connections
to their discoveries. Display their maps for all students to review, and have a whole class discussion
about what they students discovered and their thinking at this moment. Once done with this move on to
the computer simulation.
Activity: Ohm’s Law
Adapted from www.tryengineering.org
Theory:
Ohm’s Law is a mathematical equation explaining the relationship between Voltage, Current, and
Resistance within electrical circuits. It is defined as follows:
V=R*I
V = Voltage (Voltage is an electric potential difference {push} between two points on a conducting
wire. Voltage is measured in Volts and comes from various sources such as electric outlets and
batteries.)
I = Current (Current is measured in Amps. Current is charged particles which flow from the voltage
source through conductive material whenever there is a complete loop of power
source/conductors/loads.)
R = Resistance (Resistance is the opposition {to flow} that a material body offers to the passage of
an electric current. Resistance is measured in Ohms. Examples of items with resistance used in this
exercise are resistors and light bulbs.)
Ohm’s Law only holds for linear resistors (straight-line V vs. I graph). For the other devices used,
there is a power law relationship (curved-line V vs. I graph).
In a series circuit there is only one possible path from source (battery) through connectors (wires) to
the load (resistor, LED, light bulb, DC motor) and back to the source.
Batteries are a source of current and voltage. D-Cell (Alkaline) batteries have a nominal Voltage of
1.5 V. In series-connected batteries, the Voltages add, so 4 D-Cells connected in series are approx. 6
V. The current provided by a battery will vary according to the total resistance in the series circuit.
Resistor Color code & Mnemonic:
Resistors use a color code to indicate their value
Black Brown Red Orange Yellow Green Blue Violet Gray White
0
1
2
3
4
5
6
7
8
9
Better Be
Right Or
Your Great Big Venture Goes Wrong
The first 2 colors are read together as a number and the third color as a power of 10.
A resistor marked Brown Black Brown is
1
0 x 101 = 10 x 10 ohms = 100 Ω
The 4th band - in this picture Gold - means +/- 5% tolerance, so a 100 Ω resistor may be any value
from 95 Ω to 105 Ω
Silver band = +/- 10%
No color = +/- 20%
In the PhET simulation have student build the following circuit. Replacing the 200 m DCA meter with the
ammeter. See example below schematic.
Set to 200 m DCA range
XMM3
XMM4
Set to 20 DCV range
Battery
100Ω
Also note placement of digital volt meter and ammeter.
Have students use current and voltage to calculate the resistance in the circuit.
100 Ω resistor
# of
Batteries
Voltage (use
value from
actual circuit)
Current
Resistance
calculation
V
R= I
1
2
3
4
Next have student plot the resistance on a graph.
Plot the resistor voltage versus current data on this graph, using a “o” for data points. Choose an
appropriate scale to make the line as large as possible on the graph. Voltage as y-axis and current as
x-axis.
Voltage
(in Volts)
Current (in mA)
Once students have graphed their data come back together as a class and discusses any patterns they
noticed in the data. This now can lead into a discussion and Explain phase of Ohms law.