The document covers fundamental concepts of electric forces and fields, detailing the nature of electric charges, conductors, insulators, and charging processes. It explains Coulomb's law, describing the relationship between electric charges and the forces acting between them, as well as the concept of electric fields and how they function at a distance. Additionally, several sample problems illustrate the application of these concepts in calculating electric force and electric field strength.

1. GENERAL
PHYSICS 2
Second Semester

2. LESSON 1:
ELECTRIC
FORCE AND
ELECTRIC
FIELD

3. FACT OR
BLUFF
IF FACT, DANCE;
IF BLUFF, SING.

4. FACT or
BLUFF
THE SUSPENDED
NEGATIVE CHARGE
WILL REPEL TO THE
NEGATIVE CHARGE.

5. FAC
T

6. FACT or
BLUFF
THE SUSPENDED
NEGATIVE CHARGE
WILL REPEL TO THE
POSITIVE CHARGE.

7. BLUF
F

8. FACT or
BLUFF
IF THE OBJECT HAS
MORE NUMBER OF
PROTONS THAN
ELECTRONS ITS
ELECTRICAL CHARGE IS
POSITIVE.

9. FAC
T

10. FACT or
BLUFF
IF AN OBJECT HAS
EQUAL NUMBER OF
PROTONS AND
ELECTRONS IT
BECOMES NEGATIVELY
CHARGED.

11. BLUF
F

12. FACT or
BLUFF
IF AN OBJECT HAS
MORE NUMBER OF
PROTONS THAN
ELECTRONS IT IS SAID
TO BE NEUTRAL.

13. BLUF
F

14. DISCUSSION

15. The ancient Greeks discovered
as early as 600 B.C. that after
they rubbed amber with wool,
the amber could attract other
objects. Today we say that the
amber has acquired a net
electric charge or has become
charged. The word “electric” is
derived from the Greek word
elektron, meaning AMBER.

16. Benjamin Franklin (1706–
1790) suggested calling
these two kinds of
charge negative and
positive, respectively,
and these names are still
used.

18. Conductors
and
Insulators

19. Any substance that has free electrons
and allows charge to move relatively
freely through it is called a
CONDUCTOR. The moving electrons
may collide with fixed atoms and
molecules, losing some energy, but they
can move in a conductor.
SUPERCONDUCTORS allow the
movement of charge without any loss of

20. Other substances, such as glass, do
not allow charges to move through
them. These are called
INSULATORS. Electrons and ions in
insulators are bound in the
structure and cannot move easily—
as much as 1023
times more slowly
than in conductors.

22. THREE CHARGING PROCESSES
02
CHARGING
BY
CONDUCTI
ON
01
CHARGING
BY
FRICTION
03
CHARGING
BY
INDUCTION

23. Charging by Friction
01
It is when two objects are rubbed
against each other, charge transfer
takes place. One of the objects loses
electrons while the other object gains
electrons

25. Charging by Conduction
02
It is charging an uncharged object by bringing it
close and in contact with a charged object. A
charged conductor has an unequal number of
protons and electrons, hence when an uncharged
conductor is brought near it, it discharges
electrons to stabilize itself

27. Charging by Induction
03
It is the process of charging an uncharged
conductor by bringing it near a charged
conductor without any physical contact.
The law for electrostatic charge simply
tells us that as charges repel and unlike
charges attract.

29. CHARGING
The process of supplying the
electric charge to an object or
losing an electric charge from
an object.

30. Electric charge is conserved. It can
be transferred from one object to
another by moving electrons, but it
cannot be created nor destroyed.

31. ELECTRIC
FORCE AND
ELECTRIC
FIELD

32. Through the work of scientists in the late
18th century, the main features of the
ELECTROSTATIC FORCE—the existence
of two types of charge, the observation
that like charges repel, unlike charges
attract, and the decrease of force with
distance—were eventually refined, and
expressed as a mathematical formula.

33. The mathematical formula for
the electrostatic force is called
COULOMB‘S LAW after the
French physicist Charles
Coulomb (1736 1806), who
performed experiments and first
proposed a formula to calculate

34. Charles-
Augustin de
Coulomb
born June 14, 1736, Angoulême, France
—died August 23, 1806, Paris, French
physicist best known for the
formulation of Coulomb’s law, which
states that the force between two
electrical charges is proportional to the
product of the charges and inversely
proportional to the square of the
distance between them. Coulombic
force is one of the principal forces
involved in atomic reactions.

38. Sample problem for electric force:
• The electron with a charge of
1.60x10-19
C and proton with
1.60x10-19
C of a hydrogen atom
are separated by a distance of
approximately 5.3 x 10-11
m. Find
the magnitude of the electric
force.

39. Sample problem for electric force:
Given:
qe=1.60x10-19
C
qp=1.60x10-19
C
r=5.3x10-11
m
k=8.98x10^9 Nm^2/C^2
Solution:

40. Sample problem for electric force:
Two point charges, q₁ = +3.0 μC and
q₂ = -2.0 μC, are separated by a
distance of 0.15 m in air. Calculate the
magnitude and direction of the
electrostatic force between them.

41. Sample problem for electric force:
Use Coulomb's Law: F = k(q₁q₂)/r²
where
k = 8.99 × 10⁹ N m²/C²
⋅
Convert units:
q₁ = 3.0 μC = 3.0 × 10⁻⁶ C
q₂ = -2.0 μC = -2.0 × 10⁻⁶ C
r = 0.15 m

42. Sample problem for electric force:
Calculate:
Note: The negative sign indicates attraction
(opposite charges attract) The force has a
magnitude of 2.4 N and the charges attract each
other.

43. Electric Field
Electric force is described as a
non-contact force. A charged
balloon can have an attractive
effect upon an oppositely charged
balloon even
when they are not in contact. The
electric force acts over the
distance separating the two
objects. Electric force is an action-
at-a-distance force.

44. Electric Field
• Field forces explain action-at-a-distance phenomena
without physical contact.
• Charged objects create an electric field that alters
surrounding space.
• The electric field affects other charged objects in the
space, regardless of direct contact.
• The field persists whether the charged object is
present or not.
• As a charged object enters the field, the impact
becomes more noticeable.

46. The Force per Charge Ratio
Electric field strength is a vector quantity representing
the magnitude and direction of the force experienced by
a test charge in the electric field created by a source
charge. The source charge, denoted as Q, generates the
electric field. A test charge, q, is used to measure the field
strength by experiencing an electric force (symbol F). The
magnitude of the electric field is defined as the force per
unit charge on the test charge.

47. The Force per Charge Ratio
If the electric field strength is denoted by
the symbol E, then the equation can be
rewritten in symbolic form as:
In this case, the standard metric units are
Newton/Coulomb or N/C.

48. Another Electric Field Strength Formula
The above discussion pertained to defining
electric field strength in terms of how it is
measured. Now we will investigate a new
equation that defines electric field strength
in terms of the variables that affect the
electric
field strength.

49. Another Electric Field Strength Formula
Coulomb's law states that the electric force between two
charges is directly proportional to the product of their
charges and inversely proportional to the square of the
distance between their centers. When applied to our two
charges - the source charge (Q) and the test charge (q) -
the formula for electric force can be written as:

50. Another Electric Field Strength Formula
If the expression for electric force as given
by Coulomb's law is substituted for force in
the above E = F/q equation, a new
equation can be derived as shown below.

51. Another Electric Field Strength Formula
In this equation, FE is the electrostatic force
experienced by the electric charge. An
electric field is also a vector quantity. It has
the same direction as the electrostatic
force exerted on an electric charge.

52. Sample Problem 1
Calculate the electric field that a test
charge will experience on the following
distances from the source charge of 5.02 x
10-13
C.
a. Distance from source charge: 2.04 x 10-3
m
b. Distance from source charge: 1.55 x 10-12
m

53. Sample Problem 1
a.

54. Sample Problem 1
b.

55. Sample Problem 2
Compute the electric field experienced by a
test charge q = +0.80 μC from a source
charge Q = +15 μC in a vacuum when the
test charge is placed 0.20 m away from the
other charge.

56. Sample Problem 2

57. Sample Problem 2

58. Sample Problem 2