Basic Electricity
Connecting Satellites and Electronics
All you need to be an inventor is a good imagination and a
pile of junk.
-Thomas Edison
To understand electronics we must review
basic electricity.
What is Electricity?
 Everything is made of atoms
 There are 118 elements, an atom is a single part of an
element
 Atom consists of electrons, protons, and neutrons
 Electrons (- charge) are attracted to protons (+
charge), this holds the atom together
 Some materials have strong attraction and refuse to
loss electrons, these are called insulators (air, glass,
rubber, most plastics)
 Some materials have weak attractions and allow
electrons to be lost, these are called conductors
(copper, silver, gold, aluminum)
 Electrons can be made to move from one atom to
another, this is called a current of electricity.
Static Electrictiy
 Static electricity unlike current electricity that moves,
static electricity stays in one place.
 http://phet.colorado.edu/en/simulation/balloons
Van de Graaff
Dynamic, Current Electricity
 Surplus of electrons is called a
negative charge (-). A shortage
of electrons is called a positive
charge (+).
 A battery provides a surplus of
electrons by chemical reaction.
 By connecting a conductor
from the positive terminal to
negative terminal electrons will
flow.
In your CricketSAT Mission Notebook Create a Table to organize the
variables and specific characteristics of each. Always put your name
and date at the top of your table.
Quantity
Definition
Symbol/
variable
equation
Unit of measure
Resistance
Current
Voltage
Water Wheel /Electricity
Analogy
http://www.cabrillo.edu/~jmccullough/Applets/Flash/Electri
city%20and%20Magnetism/WaterAnalogy.swf
How you should be thinking
about electric circuits:
Voltage: a force that
pushes the current
through the circuit (in
this picture it would
be equivalent to
gravity)
Voltage
 A battery positive terminal (+) and a negative terminal (-). The difference in
charge between each terminal is the potential energy the battery can
provide. This is labeled in units of volts.
Water Analogy
How you should be thinking
about electric circuits:
Current: the actual
“substance” that is
flowing through the
wires of the circuit
(electrons!)
Current
 Uniform flow of electrons thru a circuit is called current.
WILL USE CONVENTIONAL FLOW NOTATION ON
ALL SCHEMATICS
How you should be thinking
about electric circuits:
Resistance: friction
that impedes flow of
current through the
circuit (rocks in the
river)
Resistance
 All materials have a resistance that is dependent on crosssectional area, material type and temperature.
 A resistor dissipates power in the form of heat
Ohm’s Law
V=IR
Georg Simon Ohm (1787-1854)
I
= Current (Amperes) (amps)
V
= Voltage (Volts)
R
= Resistance (ohms)
Ohms law
V=IR

defines the relationship between voltage, current and resistance.
 These basic electrical units apply to direct current, or alternating current.
 Ohm’s Law is the foundation of electronics and electricity.
 This formula is used extensively by electricians.
 Without a thorough understanding of “Ohm’s Law” an electrician can not
design or troubleshoot even the simplest of electronic or electrical circuits.
 Ohm established in the late 1820’s that if a voltage was applied to a resistance
then “current would flow and then power would be consumed”.
Ohm's law magic
triangle
Voltage = E or V
Current = I
Resistance = R
Ohm’s Law
If you know E and I, and wish to determine R, just
eliminate R from the picture and see what's left:
If you know E and R, and wish to determine I,
eliminate I and see what's left:
if you know I and R, and wish to
determine E, eliminate E and see what's
left:
The force or
pressure
behind
electricity
variable
Symbol
for the
unit of
measure
Ω = Ohm
milliamp or just mA
Conversions of units
•As a milliampere (milliamp or just mA) is 1/1000th of an ampere, we
can convert mA to Amps by just dividing by 1000. Another way is to take
the current in mA and move the decimal to the left three places to
accomplish the division by 1000. Here's the scoop:
275 mA / 1000 = 0.275 Amps
•Note that the decimal in 275 is to the right of the 5, and it's written as
275.0 (with a 0 added to show where the decimal is). Moving the
decimal to the left three places gets up to .275 Amps, but we usually
hang a 0 in front of the decimal.
•To convert Amps to milliAmps, just multiply by 1000 or move the
decimal to the right three places. Just the opposite of what we did here
to convert the other way.
Variable
Unit
Ω = Ohm
Break
ELECTRICAL CIRCUITS
S.MORRIS 2006
More free powerpoints at www.worldofteaching.com
Activity Sheet should include your name, date, and the following discovery information
as well as you data table and conclusion. Put in your Mission note book under the
Electronics Tab.
Discovery Activity: Open and Closed Circuits
Purpose: Evaluate and create an open and a closed circuit.
Materials: Mini light bulb, connecting wire, battery
Prediction: Make a prediction of what an open and a closed circuit would be.
Procedure:
1. Read all of the directions. Create a data table to record your results.
Include draws and explanations.
2. Manipulate the materials in many different ways to light the light bulb. Be
sure to draw and explain each trial on your data table.
Conclusion: Review and analyze your data collected from the discovery
activity. Write a conclusion, What is an open and closed circuit.
Would This Work?
Would This Work?
Would This Work?
The Central Concept: Closed
Circuit
circuit diagram
Scientists usually draw electric circuits using symbols;
cell
lamp
switch
wires
Simple Circuits
 Series circuit
 All in a row
 1 path for electricity
 1 light goes out and the
circuit is broken
 Parallel circuit
 Many paths for electricity
 1 light goes out and the
others stay on
Series and Parallel Circuit
Activity
 Create an Activity Sheet for the following activity.
 Purpose: Describe what happens to the current in a series
as more resistors are added to the circuit.
 Prediction: Predict what will happen to the current in a
series as more resistors are added.
 Procedure: Read all of the directions and create a data table
to organize the information. Include drawings in your table.
 Materials: 6 V battery, 3 light bulbs (Christmas lights will
work), 6 connector wires
Part 1 Series Circuit
 1. Connect one bulb to the battery creating a closed
circuit. Record the relative brightness and draw the
circuit.
 2. Repeat step 1 and add a second light. Record and
draw.
 3. Repeat step 2 and add a third light. Record and draw.
 4. Remove the middle light. What happened?
 5. Conclusion: Write a statement which decribes what
happens to the current in a series circuit as you add
more resistors (lights)?
1
2
PARALLEL CIRCUIT
 Place two bulbs in parallel. What do you
notice about the brightness of the bulbs?
 Add a third light bulb in the circuit. What
do you notice about the brightness of the
bulbs?
 Remove the middle bulb from the circuit.
What happened?
The CrickSAT Mission
 Reflection: Write a reflection paragraph that includes
your understanding of the following questions.
 What connections can you make between Ohm’s Law
and The CrickSAT Project? (purpose, importance,???)