Lesson 1: Electric Charge, Current and Voltage
JAYSON C. JUECO
Faculty, College of Marine Engineering
University of Cebu Lapu-lapu and Mandaue
Cebu City, Philippines
Fig. 1. Bohr Atomic Model (© 2012 Encyclopedia Britannica Inc.)
I. INTRODUCTION
A matter defines as an object that occupies space and with
finite mass. It is made up of countless dense particles moving
in a finite space. A matter breaks into a compound or an
element. A compound is a combination of two or more set
of elements. A molecule is the smallest representation of a
compound. Each element consist of a unique set of particles,
known as an Atom.
An atom is a fundamental building block of matter. It consist
of three elementary particles: the neutron n, the proton p+and
the electron e−.In the atomic lattice, neutron and proton makes
up the nucleus, while electrons orbits around the nucleus in a
fixed orbit (see F ig.1). Proton and electron are positively and
negatively charge particles.
The number of p+and e−in an atom are equal so that it
remains at a neutral state. A deviation in the number of e−
results to a charged atom, also known as an Ion. When an atom
losses an e−, it results to a positively charge atom, known as
Cation. In contrast, when atom gains an e−, it results to a
negatively charge atom, known as Anion.
An electronic model of an atom maps the e−to its shell
or orbit (see F ig.2). Each orbit or shell holds a finite number
of e−. The e−in a given shell is N= 2n2where Nis
maximum number of e−in the orbit and nis nth shell or
orbit. A valence electron lies at the outermost shell or orbit
of an atom. It plays an important role to electricity. When we
apply sufficient potential on an atom, the valence e−moves
Fig. 2. Electronic Model of an Atom (©Byjus.com)
to the neigbhoring atom causing electron flow or electricity.
We call this process as Ionization.
Each orbiting e−associates with a discrete energy level.
The energy state is directly proportional to its distance from
the nucleus. The e−closer to the nucleus has lower energy
state than at the outermost orbit (valence e−). Also, the e−
that moves out from the atomic structure experiences higher
energy state that e−in the atomic structure. Interestingly, we
see a parallelism between our solar system and the atomic
structure. In physics, the gravitational force, F=Gm1m2
d2, is
greater at object nearest to the sun than those farthest from it.
At the atomic level, e−nearest to the nucleus requires more
energy to move from one orbit to another as to valence e−.
II. E LECTRIC CHARGE
An electric charge is a fundamental quantity of an electric
circuit and measured in coulombs (C). A charge e−is negative
and equal to a magnitude of 1.602 ×10−19Cwhile p+carries
a positive charge of same magnitude. A 1Cof charge is
equal to 6.24×1018 e−. Experiments find out that only integral
multiples of electronic charge is observable in nature. These
charges can niether be created nor destroyed, only transfered
from one atom to another (Law of Conservation of Charge).
Also, unlike charges repels, and like charges attracts.
Let us have an example. Example 1: A metallic sphere and
a negatively charged rod has a charge of +4 nC and −6nC,
respectively. When the rod touches the sphere, 8.2×109
