Unit 1 - Learning Activity #1
Intro to Physical Computing - What is a Circuit?
Description
This activity introduces the concept of physical computing and the basic principles of electronics.
Students will be able to describe and illustrate their understanding of voltage, current and
resistance. At the end of this activity, students will create a project that illustrates the basic
concepts of an electrical circuit.
Suggested Duration
2 periods
Step-by-step instructions
1. What is Physical Computing?
Physical computing​, in the broadest sense, means building interactive physical systems
using computers (software and hardware) that can sense and respond to the world. In a
broad sense, physical computing is a creative framework for understanding human beings'
relationship to the digital world. (from Wikipedia)
(Modified image from Wikipedia)
In order to design physical interfaces for interactive systems, we will use a microcontroller
(simply speaking, a small computer) called “Arduino” and build electronic circuits. In order
to do that, you need to understand basic terms and concepts in electronics.
2. Basics of Voltage, Current, and Resistance ​(from SparkFun Tutorial)
● Electricity​ is the movement of electrons in a conductor. Electrons create charge, which we
can harness to do work. Your lightbulb, your stereo, your phone, etc., are all harnessing the
movement of the electrons in order to do work. They all operate using the same basic
power source: the movement of electrons. The three basic principles of electricity can be
explained using electrons, or more specifically, the charge that electrons create:
○ Voltage​ is the difference in charge between two points.
○ Current​ is the rate at which charge is flowing.
○ Resistance​ is a material’s tendency to resist the flow of charge (current).
● Understanding Voltage, Current and Resistance with a water tank analogy
○ Water amount = Charge/ moving electrons
○ Pressure = Voltage
○ Flow = Current
○ Hose Width = Resistance
Voltage (measured in Volts)
The pressure at the end of the hose can represent
voltage. The water in the tank represents charge. The
more water in the tank, the higher the charge, the
more pressure is measured at the end of the hose.
Current (measured in Amperes, or “Amps” for short)
We can think of the amount of water
flowing through the hose from the tank
as current. The higher the pressure, the
higher the flow, and vice-versa. We
measure the same amount of pressure
at the end of either hose, but when the
water begins to flow, the flow rate of the
water in the tank with the narrower hose
will be less than the flow rate of the
water in the tank with the wider hose. In
electrical terms, the current through the
narrower hose is less than the current
If we want the flow to be the same
through both hoses, we have to increase
the amount of water (charge) in the tank
with the narrower hose. This increases
the pressure (voltage) at the end of the
narrower hose, pushing more water
through the tank. This is analogous to
an increase in voltage that causes an
increase in current.
through the wider hose.
Resistance (measured in ohms, Ω)
It stands to reason that we can’t fit as much volume through a narrow pipe as we
can through a wider one at the same pressure. In this analogy, the width of the
pipe is the resistance. The narrow pipe “resists” the flow of water through it even
though the water running through it at the same pressure as the tank with the
wider pipe.
● Ohm's Law
I = V/R | V = I⋆R | R = V/I
○ V = Voltage measured in volts
○ I = Current measured in amps
○ R = Resistance measured in ohms
2. What is a Circuit?
● Circuit ​is a continuous path that connects a power source to a load through a conductive
path. All circuits have 3 main parts:
○ Power Source (i.e. Battery)
○ Conducting Path
○ Load/Resistance (i.e. LED):
○ The reason we want to build circuits is to make electricity do useful things for
us. The way we do that is by putting things in the circuit that use the current
flow to light up, make noise, run programs, etc.
○ These things are called loads, because they “load down” the power supply,
just like you’re “loaded down” when you’re carrying something. (​from
SparkFun)
● Closed Circuit​: A continuous path that connects a power source to a load or resistor
through a conductive path
● Open Circuit​: A circuit that does not allow current to flow due to a break in the conductive
path
■ A switch can be used to open and close a circuit. This is done by creating a break
from the positive terminal of a battery or from the negative terminal of the battery.
● Short Circuit​: A circuit that offers a path of least resistance that connects the positive and
negative terminals of a power source. Since current follows the path of the least resistance,
if there is an unintended path with very little resistance supplying power to a circuit, there
will be excessive current flow that causes a “short”. . When this happens the current can
get very hot because the excess energy may be released in the form of heat, so be careful
when touching the power source. A short can also damage the components of a circuit.
(Keeley, 2014)
● Common Misconceptions: Students often believe that the battery acts as the source of
whatever it is that flows around the circuit. Thus the ‘electric current’ or ‘electric charge’ or
‘electricity’ is made in the battery and flows out of the battery and around the circuit to make
the bulb light up. The correct scientific view is that the charges (or electrons) already exist
in the wires and are simply set in motion by the battery, in all parts of the circuit at the same
time.
Exercise #1: What is a Circuit?
● Ask students to illustrate their understanding of voltage, current, and resistance with a
comic, animation, or Scratch animation. Assignment must contain a minimum of three
references to the vocabulary and concepts introduced in the lesson.
● Expectations
4
Content.​ The concepts of voltage are clearly and accurately
depicted in your project.
Content.​ The concepts of current are clearly and accurately
depicted in your project.
Content.​ The concepts of resistance are clearly and
accurately depicted in your project.
Content.​ The Big Picture concept of “What is a Circuit?” is
clearly and accurately depicted in your project.
Effort.​ Student showed good behavior and attitude.
References.​ Minimum of 3 references, properly captured in
a works cited.
3
2
1
N
Presentation Quality.​ Work is neat and proofread. There are
no typos or misspelled words. Lines are clean, printed, or
drawn with detail.
Exercise #2: Paper Circuits - ​A Quick Project in Basic Electricity
● In this activity students will understand how can they create a closed electrical circuit on
paper that will light up an LED . The template for this activity is from the Circuit Sticker
Sketchbook (​Link to the book​) by Jie Qi.
● Materials:
a. CR2325 coin cell batteries
b. Multiple LEDs
c. A piece of paper or cardstock
d. Self adhesive copper tape. Aluminum foil will also work, it doesn't have the self
adhesive quality but you could use glue or tape to fix it to the paper.
e. Binder clip
f. Printouts of the template (Circuit Sticker Sketchbook Page 15)
g. Tutorial for extra help: ​Make: Simple Paper Circuits
● Directions:
1. Place copper tape over the gray lines of the Circuit Sticker sketchbook template.
Note: Apply the foil as a continuous piece, rather than separate pieces, even when
turning corners. The adhesive on the bottom side of the foil makes a weak
connection.
2. Fold the page corner along dotted line and place the battery “+” side-up over the “-”
circle.
3. Fold the corner flap over, and clip the battery in place with a binder clip.
4. When the copper tape touches the positive and the negative side of the battery,
electricity will flow through the copper tape paths.
5. Bend the LED’s legs and place each one on one of the two copper tape paths.
6. The long leg of the LED should fall on the positive path and the short leg of the LED
should fall on the negative path. To keep them in place, put copper tape over them.
7. If the circuit is properly closed, that is, if there’s electricity flowing and the
appropriate LED legs are on the correct electrical path, the LED will then turn on.
● Tips on this activity:
○ Do not let the batteries touch other as they’ll drain their power.
○ Test the battery with an LED to make sure it works.
○ When making corners or taping the LED’s legs to the copper tape, make sure they
firmly pressed so that there are no disruptions of the electrical flow. This is the most
common mistake students will do.
● Further Exploration
○ Squishy Circuits
○ How LEDs Are Made
3. Challenge Questions
Resources
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What happens when a resistor stops too much current from flowing through an LED?
How can you stop and start the flow of electricity in a circuit?
Name one kind of energy source that you can use for a circuit?
If the voltage increases, will the current (a) increase (b) decrease?
If the resistance increases, will the current (a) increase (b) decrease?
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Sparkfun: What is Electricity?
Electricity- Bill Nye the Science Guy
Sparkfun: What is a Circuit?
The History of Electricity
Sparkfun: Voltage, Current, Resistance, and Ohm's Law
Circuit Sticker Sketchbook​ by Jie Qi
Make: Simple Paper Circuits
SEP Summer PD 2016: Paper Circuits Workshop
Ohm’s Law video Part 1
Ohm’s Law video Part 2
Electrical resistance video