Basics of Electricity/Electronics
Required parts/supplies for this workshop:
Description Get it from
power supply – AC/DC wall adapter
(anything between 9 and 12V and 200-1500mA is fine)
(look in the cabinets in the Mac lab in STEW and FPRD 204)PN 355207
breadboard PN 20723
wires (solid core) PN 126360
standard LED (around 1.7V, 20mA) PN 253833
resistor 1kΩ PN 690865
capacitor 1000μF @ 25V PN 93833
NPN transistor 2N2222 PN 803268
Winkler, Basics of Electricity/Electronics Workshop, p.2
Basics of Electricity/Electronics
What is electricity?
To answer this question we will watch aninstructional film: “Principles of Electricity”,
1945, General Electric Research Laboratories. Scientific Advisors: Dr. Saul Dushman;
Dr. Roman Smoluchowski; Dr. David Harker (from: www.archive.org)
Please try to find answers to the following questions while watching the film:
• What are electrons?
• What makes them move from atom to atom?
• What is Voltage?
• What is Current?
• What is Resistance?• How do these three concepts relate to each other?
• What are conductors, what are insulators?
Electricity Basics - some answers to the questions above:
Winkler, Basics of Electricity/Electronics Workshop, p.3
For the following concepts please also consult the course book “Physical
Computing” (O’Sullivan/Igoe) chapter 1 (pp. 2-8) for a more detailed description
of the basics ofelectricity.
Current is the quantity of electrons passing a given point. The unit of current is the
Ampere. One Ampere is 6,280,000,000,000,000,000 electrons passing a point in one
second. Electrical current flows from a region of high charge or potential to a region
of low potential. To make confusion worse there exist two notions about the
direction in which current flows: ConventionalCurrent assumes that current flows out
of the positive terminal, through the circuit and into the negative terminal of the
source. This was the convention chosen during the discovery of electricity. They were
wrong! Electron Flow is what actually happens and electrons flow out of the negative
terminal, through the circuit and into the positive terminal of the source. However,
the concept ofConventional Current is still applied to almost all the circuit
schematics today, so we will use it extensively in this class.
Voltage (V or E)
Voltage is electrical pressure or force. Voltage is sometimes referred to as Potential.
Voltage Drop is the difference in Voltage between the two ends of a conductor
through which current is flowing.
The work performed by an electricalcurrent is called Power. The unit of Power is the
Conductors are not perfect. They resist to some degree the flow of current. The unit
of resistance is the Ohm.
The part of the circuit which performs work (e.g. a motor, a light bulb or a LED, etc.)
is called Load.
A set of rules that show the relationships among Current, Voltage, Power and
Resistance.Given any two of the above, one is able to calculate the other two using
the following formulas:
E = I x R
I = E / R
R = E / I
P = E x I
Direct Current Electricity
An electrical current can flow in either of two directions through a conductor. If it
flows in only one direction whether steadily or in pulses, it is called direct current
(DC). Almost all the projects in class will be poweredby DC electricity. In order to be
able to work with DC we need to convert the alternating current (AC) from the outlets
into a direct current, which we use to power our circuits. A wall adapter transforms
AC into DC, the wall adapter in our lab kit transforms 120 VAC into 9/12VDC. The
maximum current it can provide is 1000mA (1A). The wall adapter has two wires that
Winkler, Basics of...