The Nature of Electricity

Structure of the atom

The atoms which form all substances are made up of particles known as protons, neutrons and electrons. Protons are said to have a positive charge, electrons a negative charge, and neutrons no charge. Since neutrons play no part in electricity at this level of study, they will be ignored from now on.

So what is the relationship between protons and electrons? How do they form an atom? The simplest explanation is to compare an atom to our solar system, where we have a central star, the sun, around which are the orbiting planets. In the tiny atom, the protons form the central nucleus and the electrons are the orbiting particles which revolve about the nucleus in paths of concentric “shells”. The atomic number indicates of the number of electrons surrounding the nucleus for each of the known elements. Hence copper has an atomic number of 29, indicating that it has 29 orbiting electrons.

Electrons are arranged in layers at varying distances from the nucleus; those nearest the nucleus are more strongly held in place than those farthest away. If energy is applied to the atom, these distant electrons are easily dislodged from their orbits and hence are free to join those of another atom whose own distant electrons in turn may leave to join other atoms, and so on. These free or random electrons that move about the molecular structure of the material are what makes up electricity.

The electric charge

Since some atoms can lose electrons and other atoms can gain electrons, it is possible to cause a transfer of electrons from one object to another. When this takes place, the equal distribution of the positive and negative charges in each object no longer exists. Therefore, one object will contain an excess number of electrons and its charge must have a negative electric polarity. The other object will contain an excess number of protons and its charge must have a positive polarity. When a pair of objects contains the same charge, that is, both positive or both negative, the objects are said to have like charges. When a pair of bodies has different charges, that is, one body is positive while the other is negative, they are said to have unlike or opposite charges. The law of electric charges may be stated as follows:

Like charges repel each other; unlike charges attract each other.

Potential difference

The ability of a charge to do work is called its “potential”. When one charge is different from the other, there must be a difference in potential between them. Such a potential difference is generated by chemical batteries or generators.

The Nature of Electricity - Exercises

1. Match each term in column 1 to its closest meaning in column 2

1.  Electron a) Positive charge

2.  Neutron b) Same number of electrons and protons

3.  Neutral c) Negative charge

4.  Atomic number d) Number of electrons in the nucleus

5.  Free electrons e) Number of electrons in the shells

6.  Shell f) Released electrons

g) Concentric paths around the nucleus

h) Neutral charge

2. Write the word or words which most correctly complete each of the following

statements

The ability of a charge to do work is its ………………………………

When one charge is different from the other, there is a ……………. of ……………….

Like charges ……………. each other, unlike charges ………………. each other.

The electrons which make up electricity in a material are called ……… or ………… electrons.

In an atom the ……………… and ……………….. form the nucleus.

When a pair of objects contains the same charge, they are said to have ………….. charges.

3. Express each of the following in the units indicated

5,600,000 C in megacoulomb …………………………………

2.2 MC in Coulomb …………………………………

0.330 MC in kilocoulomb …………………………………

0.013 kC in Coulomb …………………………………

0.24 C in millicoulomb …………………………………

20,000 C in Coulomb …………………………………

0.25 mC in microcoulomb …………………………………

Quellen: Schaums Outlines. Basic Electricity,
Langenscheidt-Fachwörterbuch Elektrotechnik

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The Nature of Electricity : Vocabulary

The structure of the atom

substance
particle
charge
to ignore
relationship
to explain
explanation
solar system
orbit
to revolve
path
shell
to indicate
surrounding
hence
to arrange
layer
varying
far - farther - farthest
to apply
to dislodge
to join
random
The electric charge
to lose
to gain
to cause
distribution
to contain
excess
polarity
like
unlike
law
to repel
to attract
Potential difference
ability
potential