Basic Electricity Notes
EVERYTHING IS MADE OF ATOMS
Imagine a pure gold ring. Divide it in half and give one of the halves away. Keep
dividing and dividing and dividing. Soon you will have a piece so small you will not be
able to see it without a microscope. It may be very, very small, but it is still a piece of
gold. If you could keep dividing it into smaller and smaller pieces, you would finally get
to the smallest piece of gold possible. It is called an atom. If you divided it into smaller
pieces, it would no longer be gold.
Everything around us is made of atoms. Scientists so far have found only 115 different
kinds of atoms. Everything you see is made of different combinations of these atoms.
PARTS OF AN ATOM
So what are atoms made of? In the middle of each atom is a "nucleus." The nucleus
contains two kinds of tiny particles, called protons and neutrons. Orbiting around the
nucleus are even smaller particles called electrons. The 115 kinds of atoms are different
from each other because they have different numbers of protons, neutrons and electrons.
It is useful to think of a model of the atom as similar to the solar system. The nucleus is
in the center of the atom, like the sun in the center of the solar system. The electrons orbit
around the nucleus like the planets around the sun. Just like in the solar system, the
nucleus is large compared to the electrons. The atom is mostly empty space. And the
electrons are very far away from the nucleus. While this model is not completely
accurate, we can use it to help us understand static electricity.
(Note: A more accurate model would show the electrons moving in 3- dimensional
volumes with different shapes, called orbitals. This may be discussed in a future issue.)
ELECTRICAL CHARGES
Protons, neutrons and electrons are very different from each other. They have their own
properties, or characteristics. One of these properties is called an electrical charge.
Protons have what we call a "positive" (+) charge. Electrons have a "negative" (-) charge.
Neutrons have no charge, they are neutral. The charge of one proton is equal in strength
to the charge of one electron. When the number of protons in an atom equals the number
of electrons, the atom itself has no overall charge, it is neutral.
ELECTRONS CAN MOVE
The protons and neutrons in the nucleus are held together very tightly. Normally the
nucleus does not change. But some of the outer electrons are held very loosely. They can
move from one atom to another. An atom that looses electrons has more positive charges
(protons) than negative charges (electrons). It is positively charged. An atom that gains
electrons has more negative than positive particles. It has a negative charge. A charged
atom is called an "ion."
Some materials hold their electrons very tightly. Electrons do not move through them
very well. These things are called insulators. Plastic, cloth, glass and dry air are good
insulators. Other materials have some loosely held electrons, which move through them
very easily. These are called conductors. Most metals are good conductors.
How can we move electrons from one place to another? One very common way is to rub
two objects together. If they are made of different materials, and are both insulators,
electrons may be transferred (or moved) from one to the other. The more rubbing, the
more electrons move, and the larger the charges built up. (Scientists believe that it is not
the rubbing or friction that causes electrons to move. It is simply the contact between two
different materials. Rubbing just increases the contact area between them.)
Static electricity is the imbalance of
positive and negative charges.
OPPOSITES ATTRACT
Now, positive and negative charges behave in interesting ways. Did you ever hear the
saying that opposites attract? Well, it's true. Two things with opposite, or different
charges (a positive and a negative) will attract, or pull towards each other. Things with
the same charge (two positives or two negatives) will repel, or push away from each
other.
A charged object will also attract something that is neutral. Think about how you can
make a balloon stick to the wall. If you charge a balloon by rubbing it on your hair, it
picks up extra electrons and has a negative charge. Holding it near a neutral object will
make the charges in that object move. If it is a conductor, many electrons move easily to
the other side, as far from the balloon as possible. If it is an insulator, the electrons in the
atoms and molecules can only move very slightly to one side, away from the balloon. In
either case, there are more positive charges closer to the negative balloon. Opposites
attract. The balloon sticks. (At least until the electrons on the balloon slowly leak off.) It
works the same way for neutral and positively charged objects.
BASIC ELECTRONIC CIRCUITS
EXPLAINED
In this section we will discuss what a circuit is
Circuit
A circuit is a path for electrons to flow through. The path is from a power sources
negative terminal, through the various components and on to the positive terminal.
Think of it as a circle. The paths may split off here and there but they always form a line
from the negative to positive.
NOTE: Negatively charged electrons in a conductor are attracted to the positive side of
the power source.
Conductor
A conductor is a material (usually a metal such as copper) that allows electrical current to
pass easily through. The current is made up of electrons. This is opposed to an insulator
which prevents the flow of electricity through it.
Simple Circuit
If we break a circuit down to it's elementary
blocks we get:
1) A Power Source -- eg: battery
2) A Path -- eg: a wire
3) A Load -- eg: a lamp
4) A Control -- eg: switch (Optional)
5) An indicator -- eg: Meter (Optional)
Series Circuit
A series circuit is one with all the loads in a row. Like links
in a chain. There is only ONE path for the electricity to flow.
If this circuit was a string of light bulbs, and one blew out,
the remaining bulbs would turn off.
NOTE: The squiggly lines in the diagram are the symbol for
Resistors. The parallel lines are the symbol for a battery.
Parallel Circuit
A parallel circuit is one that has two or more paths for the
electricity to flow. In other words, the loads are parallel to each
other. If the loads in this circuit were light bulbs and one blew out
there is still current flowing to the others as they are still in a direct
path from the negative to positive terminals of the battery. There
are specific properties to a parallel circuit that will be described in
another section.
Combination Circuit
A combination circuit is one that has a
"combination" of series and parallel paths
for the electricity to flow. Its properties are
a synthesis of the two. In this example, the
parallel section of the circuit is like a subcircuit and actually is part of an over-all
series circuit.
VOLTAGE, CURRENT &
RESISTANCE EXPLAINED
In electronics we are dealing with voltage, current and resistance in circuits. In the next
section we'll learn that by using Ohm's Law we can determine one value by knowing the
other two (For example: Figure out Current by using Voltage and Resistance values). So
it is important to firmly grasp the basics of Voltage/Current/Resistance first.
We will describe these electrical terms using an analogy that closely resembles
electronics — HYDRAULICS.
Voltage
Voltage is the electrical force, or
"pressure", that causes current to
flow in a circuit. It is measured in
VOLTS (V or E). Take a look at
the diagram. Voltage would be the
force that is pushing the water
(electrons) forward.
Current
Current is the movement of electrical charge
- the flow of electrons through the electronic
circuit. Current is measured in AMPERES
(AMPS, A or I). Current would be the flow
of water moving through the tube (wire).
Resistance
Resistance is anything that causes an opposition to the flow of electricity in a circuit. It is
used to control the amount of voltage and/or amperage in a circuit. Everything in the
circuit causes a resistance (even wire). It is measured in OHMS ( ).
Ohm’s Law is a set of formulas used in electronics to calculate an unknown amount of
current, voltage or resistance. It was named after the German physicist Georg Simon
Ohm. Born 1787. Died 1854.
TECHNICAL DEFINITION ALERT!
Ohm's Law is a formulation of the relationship of voltage, current, and resistance,
expressed as:
Where:
V is the Voltage measured in volts
I is the Current measured in amperes
R is the resistance measured in Ohms
Therefore:
Volts = Amps times Resistance
Ohms Law is used to calculate a missing value in a circuit.
MULTIMETER ULTRA BASICS
A handheld multimeter is the most important tool you will use
in electronics. You will use it to determine
voltage/amperage/resistance in a circuit, learn the relationship
of V, I (amperage) & R to each other, troubleshoot, test
circuits and countless other tasks.
FEATURES
Here are the features you will need or should look for in a meter:
1) It should measure:
a. AC Voltage
b. DC voltage
c. Amperage
d. Resistance
e. Capacitance - Some do not have this. If so, find one that does or buy a
capacitance meter separate. Don't try to convince yourself you do not need this
feature.
2) Continuity Checker with audible beep.
3) Diode Checker with audible beep.
4) Optional but HIGHLY recommended is a frequency counter.
5) Try to get a meter with auto ranging and not one that you have to keep turning a dial
(or pushing a button) to shift to different ranges. There is nothing more annoying then
having to take your hands away from the probes to change from 300mV to +10Vs.
6) Make some alligator clips for the probe tips. My Fluke didn't come with them but I just
bought a few push-on ones later.
NAME_______________________________
SECTION__________
Electricity Review
*List the three particles and their charges that make up an atom.
Particle
Charge
___________________
__________
___________________
__________
___________________
__________
*What is electricity?
*What is a conductor?
*What is an insulator?
*Describe who the valence ring determines what type of material is produced by the
number of electrons in it.
*List six ways that we move electrons (EMF)
__________________
__________________
__________________
__________________
__________________
__________________
*Draw an atom.
Name__________________________________ Section___________
Partners’ Names___________________________________________
+
Draw a simple closed circuit.
+
Draw a controlled circuit using a SPST switch.
+
Draw a circuit controlled by two switches (SPDT).
+
-
Draw a circuit that can turn two lights on and off alternately (when one is on the other
should turn off) using only one switch.
Draw an example of a series and parallel circuit.
What is the difference between a battery and a cell?
What does AC and DC stand for?
Where does electricity want to go?
12 Volts
2 Ohms
I=20
R=2
V
10 A
100 A
5A
10 R
10 R
25 V
100 V
_____Amps
E=_____
_____R
_____V
_____R
_____A
ACROSS
2 Particles that have no charge
4 Allows electricity to flow through it freely
6 Fuses and _____ protect electrical circuits and
devices
9 The "A" in AC
10 Measures electric pressure or force
12 Electricity wants to travel to here
16 Resists the flow of electricity
17 Electricity travels at the speed of _____
(186,000miles/sec.)
19 The center of the atom
20 Measures the current of flow through a circuit
21 Multiple cells hooked up together
DOWN
1 Particles that have a positive charge
3 Particles that have a negative charge
5 The "D" in DC
7 Lightning is a form of of this type of EMF
8 Moving electrons
11 Most common form of EMF
13 The outer electron ring of an atom
14 The light should be on in this type of circuit
15 Measure the resistance in a circuit
18 A side effect of resistance
Introduction to Electricity
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CLOUD
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COMPOUND
CONDUCTOR
CONTINUITY
CONTROL
COPPER
CURRENT
DPDT
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ELECTRICITY
ELEMENT
EMF
FORCE
FUSE
GLASS
GOLD
GROUND
HYDRAULICS
INSULATOR
ION
LIGHT
LOAD
MAGNETIC
MOTOR
MULTIMETER
NEGATIVE
NEUTRAL
NUETRONS
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OHMS
PARALLEL
PATH
PLASTIC
POSITIVE
POWER
PROTONS
RESISTANCE
SERIES
SILVER
SOURCE
SPDT
SPST
STATIC
SWITCH
VALENCE
VOLTAGE
WIRE
ADDITIONAL NOTES