PHYSICS 2
ELECTRICITY: ELECTRIC
FORCE, FIELD, FLUX,
POTENTIAL, CURRENT,
RESISTANCE, EMF,
CAPACITANCE, SERIES,
PARALLEL, KIRCHOFF’S
Objectives
After completing this course, you will be able to:



1
1
Learn what Electricity is.
Explain and understand electric force, field, flux,
potential, current, resistance, EMF, capacitance,
series, and parallel.
Understand Kirchhoff‘s law.
PHYSICS 2
Electricity
 Is the set of physical phenomena associated with the presence and motion of
matter that has a property of electric charge.
 Is related to magnetism, both being part of the phenomenon
of electromagnetism, as described by Maxwell's equations.
 Various common phenomena are related to electricity, including lightning, static
electricity, electric heating, electric discharges and many others.
 Electricity is at the heart of many modern technologies, being used for:
o Electric power where electric current is used to energize equipment;
o Electronics which deals with electrical circuits that involve active electrical
components such as vacuum tubes, transistors, diodes and integrated
circuits, and associated passive interconnection technologies.
Electric Force
 Electric force is exerted between any two charged objects. Objects with the same
charge, both positive and both negative, will repel each other, and objects with
opposite charges, one positive and one negative, will attract each other.
Field
 A field is a physical quantity, represented by a number or tensor, that has a value
for each point in space and time. For example, on a weather map, the
surface temperature is described by assigning a real number to each point on a
map; the temperature can be considered at a certain point in time or over some
interval of time, to study the dynamics of temperature change. A surface wind
map, assigning an arrow to each point on a map that describes the wind speed
and direction at that point, would be an example of a 1-dimensional tensor field,
i.e. a vector field. Field theories, mathematical descriptions of how field values
change in space and time, are ubiquitous in physics.
Flux
 Flux is the presence of a force field in a specified physical medium, or the flow of
energy through a surface. The term applies to any electrostatic field and any
magnetic field. Flux is depicted as "lines" in a plane that contains or intersects
electric charge poles or magnetic poles.
Potential
 The definition of potential is having the power or being capable of
happening. potential energy is the energy a charge has due to its position relative
to other charges.
 Potential in physics can be defined as the work done in bringing a unit positive
test charge from infinity to a given point.
Current
 Current is a flow of electrical charge carriers, usually electrons or electrondeficient atoms. Physicists consider current to flow from relatively positive points
2 to relatively negative points; this is called conventional current or
2
PHYSICS 2
Franklin current. Electrons, the most common charge carriers, are negatively
charged.
Resistance
 Resistance is a measure of the opposition to current flow in an electrical
circuit. Resistance is measured in ohms, symbolized by the Greek letter omega
(Ω).
EMF
 Electromotive force, abbreviation E or emf, energy per unit electric charge that is
imparted by an energy source, such as an electric generator or a battery
Capacitance
 Capacitance is expressed as the ratio of the electric charge on each conductor to
the potential difference (i.e., voltage) between them. The capacitance value of
a capacitor is measured in farads (F), units named for English physicist Michael
Faraday (1791–1867). A farad is a large quantity of capacitance.
Series
 A series circuit is a circuit in which resistors are arranged in a chain, so the
current has only one path to take. The current is the same through each resistor.
Parallel
 A parallel circuit is a closed circuit in which the current divides into two or more
paths before recombining to complete the circuit. Each load connected in a
separate path receives the full circuit voltage, and the total circuit current is equal
to the sum of the individual branch currents
Kirchoff’s
 Kirchhoff's first law is that the algebraic sum of currents in a network of
conductors meeting at a point (or node) is zero. The second law is that in a
closed circuit, the directed sums of the voltages in a closed system is zero.
Kirchhoff's three laws of spectroscopy
1. A solid, liquid, or dense gas excited to emit light will radiate at all wavelengths
and
2. Thus produce a continuous spectrum.
3. A low-density gas excited to emit light will do so at specific wavelengths and this
produces an emission spectrum. (See also: emission spectrum)
4. If light composing a continuous spectrum passes through a cool, low-density gas,
the result will be an absorption spectrum.
3
3
PHYSICS 2
Video links:
What is electricity? - Electricity Explained
 https://www.youtube.com/watch?v=ru032Mfsfig
Electric Charge: Crash Course Physics
 https://www.youtube.com/watch?v=TFlVWf8JX4A
Electric Current & Circuits Explained, Ohm's Law, Charge, Power,
Physics Problems, Basic Electricity
 https://www.youtube.com/watch?v=r-SCyD7f_zI
Ohm's Law
 https://www.youtube.com/watch?v=_rSHqvjDksg
Electric Charge and Electric Fields
 https://www.youtube.com/watch?v=VFbyDCG_j18
Electric Field Physics Problems - Point Charges, Tension Force,
Conductors, Square & Triangle
 https://www.youtube.com/watch?v=j6sDLnNuFW0
Reference:



4
4
Jones, D.A. (1991), "Electrical engineering: the backbone of
society", IEE Proceedings A - Science, Measurement and
Technology, 138 (1): 1–10
Moller, Peter; Kramer, Bernd (December 1991), "Review:
Electric Fish", BioScience, American Institute of Biological
Sciences, 41 (11): 794–96 [794]
Bullock, Theodore H. (2005), Electroreception, Springer,
pp. 5–7,