Electricity is
the set of physical
phenomena
associated with the presence and flow of electric
charge.
In
physics, energy
is defined as the amount of work that can be performed by force,
whereas power is defined as the rate at which work is performed.
Electric
potential is
the
capacity of an electric field to do work
on
an electric
charge,
typically measured in volts
(V)
Electric
current is
a movement or flow of electrically charged particles, typically
measured in amperes
(A)
An
ampere-hour
or
amp-hour
(Ah)
is a unit of electric
charge,
equal to the charge transferred by a steady current of one ampere
flowing
for one hour. The
ampere-hour is frequently used in measurements of electrochemical
systems
such as electroplating
and
electrical
batteries..
An AA
size
dry
cell
has
a capacity of about 2 or 3 ampere-hours. Automotive car
batteries
vary
in capacity but a large automobile propelled by an internal
combustion engine would have about a 50 ampere-hour battery capacity.
A
volt-ampere
(VA)
is the unit used for the apparent
power
in
an electrical
circuit
equal
to the product of root-mean-square
voltage
and
root-mean-square
current.
In
direct current (DC) circuits, this product is equal to the real
power
(active
power in watts.)
Volt-amperes are useful only in the context of alternating
current
(AC)
circuits (sinusoidal
voltages
and currents of the same frequency). Some devices, including
uninterruptible
power supplies (UPSs),
have ratings both for maximum volt-amperes and maximum watts. The VA
rating is limited by the maximum
permissible current, and the watt rating by the power-handling
capacity of the device.
One watt
(W) is
defined as the energy consumption rate of one joule per second.
The
joule
is
a derived
unit
of
energy,
work,
or amount of heat
in
the International
System of Units.
It
is equal to the energy transferred or work done when applying a force
of
one newton
through
a distance of one metre,
or in passing an electric current
of
one ampere
through
a resistance
of
one ohm
for
one second. One
newton is the force needed to accelerate one kilogram
of
mass at the rate of one metre
per second squared. Ohm
is
defined as a resistance between two points of a conductor when a
constant potential difference of 1
volt,
applied to these points, produces in the conductor a current of 1
ampere. One
watt
is
also defined as the current flow of one ampere with voltage of one
volt.
The kilowatt (kW) is equal to one thousand watts and the megawatt (MW) is equal to one million watts, the gigawatt (GW) equal to one billion watts..
The kilowatt (kW) is equal to one thousand watts and the megawatt (MW) is equal to one million watts, the gigawatt (GW) equal to one billion watts..
The kilowatt-hour (kWh) is a unit of energy equivalent to one kilowatt (1 kW) of power expended for one hour. An electrical load (e.g. a lamp, toaster, electric motor, etc.) has a rated "size" in watts. This is its running power level, which equates to the instantaneous rate at which energy must be generated and consumed to run the device. The world currently consumes 20 trillion kWh of energy annually. How much energy is consumed at that rate depends on how long you run the device. However, its power level requirements are basically constant while running. The unit of energy for residential electrical billing, kilowatt-hours, integrates changing power levels in use at the residence over the past billing period (nominally 720 hours for a 30-day month), thus showing cumulative electrical energy use for the month.
A
multimeter
or
a multitester,
also known as a VOM
(Volt-Ohm
meter or Volt-Ohm-milliammeter), is an electronic
measuring
instrument
that
combines several measurement functions in one unit. A typical
multimeter would include basic features such as the ability to
measure voltage,
current,
and resistance.
Image: http://www.tekmoz.com
Comparison
of African and World electricity tariffs in US cents per kWh for the
years 2011 and 2014
| # | Country | Cost (USc/kWh) | YoY % Change |
| 1 | Italy | 21.01 | -1.7% |
| 2 | Germany | 19.21 | -1.7% |
| 3 | United Kingdom | 15.40 | 3.5% |
| 4 | Portugal | 13.84 | 0.1% |
| 5 | Spain | 13.64 | -7.0% |
| 6 | Belgium | 12.68 | 3.6% |
| 7 | Slovakia | 12.55 | -2.9% |
| 8 | France | 10.74 | 3.8% |
| 9 | Czech Republic | 10.47 | -7.7% |
| 10 | Poland | 10.46 | 5.5% |
| 11 | Austria | 10.44 | -5.5% |
| 12 | Netherlands | 10.08 | -8.5% |
| 13 | United States | 10.00 | 7.1% |
| 14 | Australia | 9.71 | -23.3% |
| 15 | South Africa | 8.97 | 7.5% |
| 16 | Finland | 8.59 | -1.8% |
| 17 | Canada | 8.11 | 2.5% |
| 18 | Sweden | 7.87 | -2.4% |
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