GENERAL PHYSICS 2
ELECTROSTACTICS inversely proportional to the square of
The study of all phenomena associated the distance between them.
with electric charges at rest. Charges
reach their equilibrium positions rapidly
because the electric force is extremely
strong.
Processes of Charging
1. Charging by Friction – results when
two different materials are rubbed
together. The material that will either
become positively or negatively
charged depends on its electron
affinity. Electron affinity is a measure
of the attraction of an atom to an
electron, or the tendency of an atom
to become negatively charged.
Materials with higher electron affinity
are capable of gaining electrons from
those of lower electron affinity.
2. Charging by Conduction – requires
physical contact between a charging ELECTRIC FIELD
body and a neutral body. The sign of Electric force is a
the charged acquired by the neutral noncontact force. An
body is the same with that of the electric charge q can
charged body. A neutral body exert force on. Other
becomes positively charged when charged objects even
charged by positively charged body. though they are at the
Likewise, it becomes negatively same distance away. The
charged when charged by a space surrounding a charged body is
negatively charged body. called an electric field.
3. Charging by Induction - a neutral ELECTRIC FLUX
body may also be charged without Electric field can be quantitatively
physical contact with a charged body. described using the concept of electric
The negative charges on the neutral flux. The word flux comes from the Latin
are attracted toward the charging word fluxus meaning “flow”. Electric flux
body if the latter is positive. They are ( ) is a measure of the number of fields
repelled, from the charging body if it lines passing through a surface.
is negatively charged. This effect is
known as polarization.
COULOMBS LAW CAPACITORS AND CAPACITANCE
the magnitude of the electrical force A capacitor is a devise for storing
between two charged particles is charges. A capacitor (originally known
directly proportional to the product of as a condenser) is a passive two-terminal
the magnitudes of the charges and electrical component used to store
GENERAL PHYSICS 2
energy electrostatically in an electric
field.
Capacitance is the ability of a capacitor
to store charges. The capacitance (C) of
a capacitor is mathematically defined as
the ratio of the amount of the charge (q)
in one plate to the potential difference
(V) between the plates. In symbols,
The SI unit of capacitance is
farad (F) named after Michael Faraday.
Note that 1 farad is equal to 1 coulomb
per volt.
a. The area of the plates. The bigger
the plates, the greater the capacitance.
b. The distance between the plates.
The closer the plates to one another, the
greater the capacitance.
c. The insulating material or
dielectric between them. The
capacitance is determined in terms of
the material’s permittivity constant () –
the higher the, the greater the
capacitance.
ELECTRIC CURRENT (I)
Electric current, or simply current, is the
amount of charge passing through any
point in a conductor per unit time. In
symbols, .
1. Conventional Current vs.
Electron Current
GENERAL PHYSICS 2
The direction of current flow is from the
positive (+) terminal to the negative (-)
terminal of a power source.
Conventional Current
Moves from the negative (-) terminal to
the positive (+) terminal. Electron
Current
2. Direct Current vs. Alternating
Current
The current that travels in one direction
(at all times) is called direct current
(DC) that changes directions at a regular
interval (normally 60 times in one
second) is called alternating current
(AC).
2. Factors Affecting the
Resistance of a Uniform Wire
(a) Cross-sectional Area – larger areas
offer less resistance;
ELECTRICAL RESISTANCE (R) (b) Length – Longer materials have
Electrical resistance, or simply greater resistance;
resistance, is the opposition of a
(c) Kind of material – Iron has more
material to the flow of electric current.
electrical resistance than a
The SI unit of resistance is the ohm (Ω),
geometrically similar copper conductor;
named after Georg Simon Ohm. and
1. Color Code for Resistors (d) Temperature - the higher
temperatures usually result in high
resistances.
3. Ohmic and Nonohmic
Resistance
Resistance is also defined as the ratio of
voltage to the resulting current. In
symbols,
GENERAL PHYSICS 2
F = force, q = charge, v = velocity, B =
magnetic field
AMPERE’S LAW
Ampere's Law states that the magnetic
field around a closed loop is directly
proportional to the total electric current
ELECTROMOTIVE FORCE (EMF)
passing through the loop.
VS POTENTIAL DIFFERENCE OR
VOLTAGE (V)
EMF is electrically charged particles
because of the separation of electrons
from the atoms by consuming some
types of energy such as chemical,
mechanical, or light. EMF = W/Q
Potential Difference or Voltage on the
other hand is the difference of the
electrical states on the poles. In a closed
electrical circuit, electrons move from
the negative half to the positive half.
Electrical voltage is referred to the work
performed by the electric force in
moving the charge from one point of the
field to another. V = W/Q or V = E/Q
MAGNETISM
Magnetism is the ability of a magnetic
material to attract other magnetic
materials. A material possessing this
ability is called a magnet. A magnet may
be natural or artificial. The most
common natural magnet is lodestone.
MAGNETIC FIELDS AND
MAGNETIC FIELD LINES
A magnetic field is a region of space,
which has the ability to exert a magnetic
force on
magnetic
dipoles and on
moving electric
charges.
