Basics of Electricity
10
Two examples will help.
1) If you discharge a battery pack into light bulbs the energy stored in the battery's
chemistry was converted to heat in the battery's chemical reaction the wiring and the light
bulb filaments.
2) In an electric motor powered plane, energy from the battery converts to
heat energy
in
wires, connectors, the electronic components in the Electronic Speed Control, the wires in
the motor armature, the brushes, the motor bearings and lubricant and the air the prop and
plane fly through AND to
potential energy
that has been stored by the height the plane's
mass is above the ground AND to
kinetic energy
stored in the speed of the plane's mass.
If you measured all the heat generated and other stored energies, it would equal that
previously stored in the battery. That's the conservation.
Inefficiency in a process like this means some energy went someplace you didn't want it to
like the wires, bearings, ESC and brushes. You wanted it all delivered to the prop.
In battery charging, energy from the charger is delivered as a current into a battery where it
is converted to a charge stored in the battery's chemistry. In a perfect rechargeable battery
no energy would go anyplace else. In reality it does, like to heat, so battery charging is not
100 % efficient.
What you can learn from all of this is that your options for an electric powered model's
capabilities must consider all the places energy will be used.
Learning some basic things about potential and kinetic energy as well as Newton's second
Law of motion in a simple physics text book will give you powerful tools to evaluate an
electric model capabilities.
4.8
About Units
Small amounts of current and voltage are usually measured in milliamps or millivolts
where “milli” is a Greek abbreviation meaning “one thousandth of.” For example, 10 mA
means ten – one thousandths of one Amp, which is written as 0.01 Amps. 1000 mA is
another way to write 1 A. Similarly, 0.001 V is one thousandth of one volt. Milli is a
widely used prefix. E.g. 3000 mAh is another way to write a charge of 3 Ah.
"Watt's Up" & "Doc Wattson" Watt Meter and Power Analyzer User's Manual
RC Electronics, Inc.
