This document covers key concepts in electricity including electric charge, Coulomb's law, electric fields, potential difference, and capacitors. It describes three experiments showing that like charges repel and unlike charges attract. It defines the coulomb as the unit of electric charge and explains that electric charge is found in protons, electrons, and neutrons in atoms. It also summarizes that the electric field is the "alteration of space" caused by a charge, conductors allow electric charge to flow easily, capacitors store energy in an electric field between charges, and capacitance depends on the geometry and materials of a capacitor.

1. Electricity
Physics 2

2. Topic Outline
• Electric Charge
• Coulomb’s Law
• Electrical Conduction
• Electric Field
• Potential Difference
• Capacitor

3. Experiment 1
A rubber rod stroked
with fur becomes
negatively charged; two
negatively charged
objects repel each other.

4. Experiment 2
A rubber rod stroked
with silk becomes
positively charged; two
positively charged
objects repel each other.

5. Experiment 3
Objects with unlike
charges attracts each
other.

6. In Summary:
Like charges repel; Unlike charges attract.

7. Electric Charge
Three types of particles are
found in atoms, the positively
charged proton, the negatively
charged electron, and the
neutral (that is, uncharged)
neutron.
The proton and electron have
exactly equal amounts of
charge, though of opposite
sign.
Neutrons and protons have
nearly the same mass, which is
almost 2000 times greater
than the electron mass.

8. Conservation of Charge
The net electric charge in an isolated system
remains constant.

9. Coulomb’s Law

10. The Coulomb
The unit of electric charge is the coulomb (abbreviated C). All
charges, of either sign, occur in multiples of fundamental
electron charge e of 1.6 x 10‐19 coulomb.

11. Electricity and Conduction
An electric current is a flow of charge.
Nearly all substances fall into two categories:
conductors, through which charge can flow easily,
insulators, through which charge can flow only with
great difficulty.
Metals, many liquids, and plasmas (gases whose
particles are charged) are conductors. Nonmetallic
solids, certain liquids, and gases whose molecules are
electrically neutral are insulators.

12. Electric Field
When an electric charge is present somewhere, the properties of
space around it altered in such a way that another charge brought to
this region will experience a force there. The “alteration space” caused
by a charge at rest is called electric field.

13. Example:

14. Potential Difference
The potential difference between two points is the
work per unit charge that must be done to take charge
from one points to the other. The unit of potential
difference is the volt which is equal to 1 J/C.
The volt is named after the Italian physicist Alessandro
Volta (1745 – 1827), who invented the battery.

15. The Electron Volt
The electron volt (abbreviated eV) is the customary energy
unit in atomic and nuclear physics. By definition 1.00 eV is
the energy gained by an electron that has been accelerated
through a potential difference of 1.00 volt

16. Capacitor
A capacitor is a system of conductors that stores energy in the form of
an electric field between the charges.
An example of a capacitor is a pair of parallel metal plates of area A
that are a distance d apart. Let us imagine that we create an electric
field between them by bringing electrons from one plate to the other
until a total charge of Q has been transferred. When we are finished,
there will be a potential difference of V between the plates.

17. Capacitance

18. Parallel‐Plate Capacitor

19. Example:

20. Capacitors in Series

21. Capacitors in Parallel

22. REFERENCE:
Modern Technical Physics 6th Edition by
Arthur Beiser
Copyright © 1992 by Addison‐Wesley
Publishing Company, Inc.