1. Basic Electrical DC
Circuit Theory
Science Olympiad 2013

2. It all starts with the
ATOM
An ATOM is
composed of three
parts:
PROTONS
NEUTRONS
ELECTRONS
The tightly –
bound clump of
protons &
neutrons in the
center of the
ATOM is called the
nucleus
THE ELEMENT OF CARBON

3. PROTONS = IDENTITY
The tightly – bound clump of protons & neutrons in
the center of the ATOM is called the nucleus. The
number of protons in the nucleus is what determines
its elemental identity; in this case CARBON.
THE ELEMENT OF
CARBON

4. NEUTRONS = MASS
If neutrons are added or gained in the nucleus the
ATOM will retain the same chemical identity, but its
MASS will change slightly and it may acquire strange
nuclear properties such as radioactivity

5. ELECTRONS =
ATTRACTION
Electrons, unlike protons and neutrons, have more
freedom to move around. In fact they can be knocked
out of position and leave an ATOM entirely; if that
happens the ATOM keeps its chemical identity but a
very important imbalance happens.
electrons & protons are unique
because they are attracted to one
another over a distance. It is this
attraction over distance which
causes the attraction between
rubbed objects, where electrons
are moved away from their original
atoms to reside around atoms of
THE ELEMENT OF another object.
CARBON

6. POSITIVE & NEGATIVE
CHARGES
ELECTRONS (-) PROTONS (+)
Have a NEGATIVE Have a POSITIVE
charge charge
An object whose An object whose
atoms have atoms are lacking
received a surplus electrons is
of electrons is positively charged
negatively
charged
THE ELEMENT OF CARBON
In equal numbers within an atom, they counteract each other's presence so that the net charge within the atom
is zero. This is why the picture of a carbon atom has six electrons: to balance out the electric charge of the six
protons in the nucleus. If electrons leave or extra electrons arrive, the atom's net electric charge will be
imbalanced, leaving the atom "charged" as a whole, causing it to interact with charged particles and other
charged atoms nearby. Neutrons are neither attracted to or repelled by electrons, protons, or even other
neutrons, and are consequently categorized as having no charge at all.

7. What is A Circuit?
Electrons flow from the zinc
casing to the carbon rod,
lighting the bulb in the
process. The zinc casing acts
as a negative electrode; the
carbon rod acts as a positive
electrode. The ammonium
chloride paste acts as the
electrolyte and the carbon and
the manganese dioxide
mixture around the carbon rod
extends the battery's life.
Let's take an example of a battery, for now. The battery has a positive (+) end, and a
minus ( - ) end. When you touch a wire onto both ends of the battery at the same time,
you have created a circuit. What just happened? Current flowed from one end of the
battery to the other through your wire. Therefore, our definition of circuit can simply be a
never-ending looped pathway for electrons (the battery counts as a pathway!).

8. Requirements for a
Circuit
Must have a closed conducting path which extends
from the positive terminal to the negative terminal.
Think of this as a circle or a loop
ALL connections must be made by conducting
materials capable of carrying charge.

9. Current
This battery takes these negatively charged electrons from a chemical reaction inside the battery,
pushes them out of the negative end of the battery, and into the wire. These electrons will then
bump electrons in the atoms of the wire over and over until finally electrons arrive back at the
positive end of the battery. Elements which allow this process of "bumping" those electrons on
over determines how conductive the element is. So, when there's a current, it's just electrons
bumping each other from atom to atom and flowing on.

10. Sources
http://scioly.org/wiki/index.php/Circuit_Lab_(Episode
s)
http://www.allaboutcircuits.com/vol_1/chpt_1/1.html