Leyden Jar, Electric Charge, Galvanic Cell, Voltaic Pile, Anions, Cations, Daniell Cell, Zinc-Carbon Battery and Alkaline Battery

Posted by PITHOCRATES - December 25th, 2013

Technology 101

(Originally published December 19th, 2012)

Luigi Galvani made a Dead Frog’s Leg Twitch when he hit it with the Electric Discharge Shock from a Leyden Jar

The field of electricity took off with friction generators.  Dragging something across another substance to produce an electrical charge.  Like sliding out of your car on a dry winter day.  Producing an electric discharge shock just before your hand touches the metal door to close it.  Atoms in materials are electrically neutral.  There are an equal number of positive particles (protons) and negative particles (electrons).  Friction can transfer some of those electrons from one surface to another.  Leaving one surface with a net positive charge.  And the other with a net negative charge.  These charges equalize after that electric discharge shock.  Returning the atoms in these materials to an electrically neutral state.

Further exploration of static electric charge led to the development of the Leyden jar.  A precursor to the modern capacitor.  A glass jar with metal foil on the inside and outside of a glass bottle.  The foil sheets act as plates.  The glass as a dielectric.  An electrode attached to one plate received an electric charge from a friction generator.  The other plate was grounded.  The dielectric helped the plates hold an electric charge.  Benjamin Franklin did a lot of experiments with the Leyden jar.  He noted how multiple Leyden jars could hold a greater charge.  Commenting that it was like a battery of cannons.  Giving us the word battery for an electrical storage device.

Luigi Galvani made a dead frog’s leg twitch when he zapped it with the electric discharge shock from a Leyden jar.  Furthering his experiments Galvani found that he could reproduce the twitching by placing the frog’s leg between two different types of metals.  Creating a galvanic cell.  Which created an electric current.  Alessandro Volta recreated this experiment while substituting the frog tissue with cardboard soaked in salt water (an electrolyte).  Creating the voltaic cell.  Piling one voltaic cell onto another created a Voltaic Pile.  Or as we call it today, a battery.

A Daniell Cell created a Current by Stripping away Electrons from one Electrode and Recombining them on Another

What Galvani and Volta discovered was a chemical reaction that caused an electric current.  The Voltaic Pile, though, had a limited life.  To improve on it John F. Daniell added a second electrolyte.  Creating the Daniell Cell.  Which extended the life of a battery charge.  Allowing it to do useful work.  Becoming the first commercially successful battery.  Powering our first telegraphs and telephones.  Even finding their way into our homes operating our doorbells for a century or so before Nikola Tesla brought alternating current electric power to our homes.

The chemical reaction in a Daniell Cell created an electric current by stripping away electrons from one metal electrode in a solution (anode oxidation).  And recombining electrons onto another electrode of a different metal in a different solution (cathode reduction).  Each electrode is in an electrolyte solution.  In a copper-zinc Daniell Cell the anode is typically in a solution of zinc sulfate.  And the cathode is in a copper sulfate solution.  A salt bridge or porous membrane connects the different electrolytes.  When an electric load is connected across the ‘battery’ electrodes it completes the electrochemical system.

Each electrolyte contains ions.  Atoms with a net positive or negative charge.  Positive ions are cations.  Negative ions are anions.  The cathode attracts cations.  Where they combine with free electrons to return to a neutral state.  The anode attracts anions.   Where they give up their extra electrons to return to a neutral state.  This chemical activity dissolves the zinc electrode.  And deposits copper on the copper electrode.  (This electrolysis is the basis for the metal plating industry.)  It is the dissolving of the anode that gives up electrons that travel from one electrode through the electric load to the other electrode.  Doing work for us.  By lighting our flashlights.  Or powering our portable radio.  When the anode dissolves to the point that it cannot give up anymore electrons the chemical reaction stops.  And we have to replace our batteries.

An Alkaline Battery will produce more Useable Power and have a longer Shelf Life than a Zinc-Carbon Battery

Of course, the zinc-carbon batteries we use for our flashlights and radios are not wet cells.  They’re dry cells.  Instead of an electrolyte solution the common battery is made up of dry components.  The zinc anode is the battery casing.  Just inside the battery zinc casing is a paper layer impregnated with a moist paste of acidic ammonium chloride.  This separates the zinc can from a mixture of graphite powder and manganese (IV) oxide (pyrolusite).  In the center of the battery is a carbon rod.  The zinc casing is the negative electrode (anode) and the carbon rod is the positive electrode (the cathode).  The chemical reactions are the
same as they are with the wet cell.  The zinc casing (the anode) becomes thinner over time.  When holes begin to appear the battery will leak creating a sticky mess.  As you no doubt experienced when taking an old set of batteries out of a flashlight that hasn’t been used in years.

An alkaline battery looks similar to a zinc-carbon battery.  But there are many differences.  Instead of an acidic ammonium chloride electrolyte an alkaline battery uses an alkaline potassium hydroxide electrolyte.  The little nub (positive terminal) on top of the battery does not connect to a carbon rod in the center of the battery.  It connects to the outer casing.  Inside this casing is a mixture of graphite powder and manganese (IV) oxide (pyrolusite).  Then a barrier to keep the anode and cathode materials from coming into contact with each other.  But lets ions pass through.  On the other side of the barrier is the anode.  A gel of the alkaline potassium hydroxide electrolyte containing a dispersion of zinc powder.  In the middle of the battery is a metal rod that acts as a current pickup that connects to the bottom of the battery (the negative terminal).

Alkaline batteries are the most popular batteries today.  Because they have a higher energy density than a zinc-carbon battery.  Meaning that an alkaline battery will produce more useable power than a comparable sized zinc-carbon battery.  And they have a longer shelf life.  But with these benefits comes costs.  They can leak a caustic potassium hydroxide.  An irritant to your eyes and skin.  As well as your respiratory system.  As they age they can produce hydrogen gas.  Which can rupture the casing.  If a battery leaks potassium carbonate (a crystalline structure) can grow.  If this crystalline structure reaches the copper tracks of a circuit board it will oxidize the copper and metallic components.  Damaging electronic devices.  But the benefits clearly outweigh the risks.  As about 80% of all batteries sold in the U.S. are alkaline batteries.

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Leyden Jar, Electric Charge, Galvanic Cell, Voltaic Pile, Anions, Cations, Daniell Cell, Zinc-Carbon Battery and Alkaline Battery

Posted by PITHOCRATES - October 2nd, 2013

Technology 101

(Originally published December 19th, 2012)

Luigi Galvani made a Dead Frog’s Leg Twitch when he hit it with the Electric Discharge Shock from a Leyden Jar

The field of electricity took off with friction generators.  Dragging something across another substance to produce an electrical charge.  Like sliding out of your car on a dry winter day.  Producing an electric discharge shock just before your hand touches the metal door to close it.  Atoms in materials are electrically neutral.  There are an equal number of positive particles (protons) and negative particles (electrons).  Friction can transfer some of those electrons from one surface to another.  Leaving one surface with a net positive charge.  And the other with a net negative charge.  These charges equalize after that electric discharge shock.  Returning the atoms in these materials to an electrically neutral state.

Further exploration of static electric charge led to the development of the Leyden jar.  A precursor to the modern capacitor.  A glass jar with metal foil on the inside and outside of a glass bottle.  The foil sheets act as plates.  The glass as a dielectric.  An electrode attached to one plate received an electric charge from a friction generator.  The other plate was grounded.  The dielectric helped the plates hold an electric charge.  Benjamin Franklin did a lot of experiments with the Leyden jar.  He noted how multiple Leyden jars could hold a greater charge.  Commenting that it was like a battery of cannons.  Giving us the word battery for an electrical storage device.

Luigi Galvani made a dead frog’s leg twitch when he zapped it with the electric discharge shock from a Leyden jar.  Furthering his experiments Galvani found that he could reproduce the twitching by placing the frog’s leg between two different types of metals.  Creating a galvanic cell.  Which created an electric current.  Alessandro Volta recreated this experiment while substituting the frog tissue with cardboard soaked in salt water (an electrolyte).  Creating the voltaic cell.  Piling one voltaic cell onto another created a Voltaic Pile.  Or as we call it today, a battery.

A Daniell Cell created a Current by Stripping away Electrons from one Electrode and Recombining them on Another

What Galvani and Volta discovered was a chemical reaction that caused an electric current.  The Voltaic Pile, though, had a limited life.  To improve on it John F. Daniell added a second electrolyte.  Creating the Daniell Cell.  Which extended the life of a battery charge.  Allowing it to do useful work.  Becoming the first commercially successful battery.  Powering our first telegraphs and telephones.  Even finding their way into our homes operating our doorbells for a century or so before Nikola Tesla brought alternating current electric power to our homes.

The chemical reaction in a Daniell Cell created an electric current by stripping away electrons from one metal electrode in a solution (anode oxidation).  And recombining electrons onto another electrode of a different metal in a different solution (cathode reduction).  Each electrode is in an electrolyte solution.  In a copper-zinc Daniell Cell the anode is typically in a solution of zinc sulfate.  And the cathode is in a copper sulfate solution.  A salt bridge or porous membrane connects the different electrolytes.  When an electric load is connected across the ‘battery’ electrodes it completes the electrochemical system.

Each electrolyte contains ions.  Atoms with a net positive or negative charge.  Positive ions are cations.  Negative ions are anions.  The cathode attracts cations.  Where they combine with free electrons to return to a neutral state.  The anode attracts anions.   Where they give up their extra electrons to return to a neutral state.  This chemical activity dissolves the zinc electrode.  And deposits copper on the copper electrode.  (This electrolysis is the basis for the metal plating industry.)  It is the dissolving of the anode that gives up electrons that travel from one electrode through the electric load to the other electrode.  Doing work for us.  By lighting our flashlights.  Or powering our portable radio.  When the anode dissolves to the point that it cannot give up anymore electrons the chemical reaction stops.  And we have to replace our batteries.

An Alkaline Battery will produce more Useable Power and have a longer Shelf Life than a Zinc-Carbon Battery

Of course, the zinc-carbon batteries we use for our flashlights and radios are not wet cells.  They’re dry cells.  Instead of an electrolyte solution the common battery is made up of dry components.  The zinc anode is the battery casing.  Just inside the battery zinc casing is a paper layer impregnated with a moist paste of acidic ammonium chloride.  This separates the zinc can from a mixture of graphite powder and manganese (IV) oxide (pyrolusite).  In the center of the battery is a carbon rod.  The zinc casing is the negative electrode (anode) and the carbon rod is the positive electrode (the cathode).  The chemical reactions are the
same as they are with the wet cell.  The zinc casing (the anode) becomes thinner over time.  When holes begin to appear the battery will leak creating a sticky mess.  As you no doubt experienced when taking an old set of batteries out of a flashlight that hasn’t been used in years.

An alkaline battery looks similar to a zinc-carbon battery.  But there are many differences.  Instead of an acidic ammonium chloride electrolyte an alkaline battery uses an alkaline potassium hydroxide electrolyte.  The little nub (positive terminal) on top of the battery does not connect to a carbon rod in the center of the battery.  It connects to the outer casing.  Inside this casing is a mixture of graphite powder and manganese (IV) oxide (pyrolusite).  Then a barrier to keep the anode and cathode materials from coming into contact with each other.  But lets ions pass through.  On the other side of the barrier is the anode.  A gel of the alkaline potassium hydroxide electrolyte containing a dispersion of zinc powder.  In the middle of the battery is a metal rod that acts as a current pickup that connects to the bottom of the battery (the negative terminal).

Alkaline batteries are the most popular batteries today.  Because they have a higher energy density than a zinc-carbon battery.  Meaning that an alkaline battery will produce more useable power than a comparable sized zinc-carbon battery.  And they have a longer shelf life.  But with these benefits comes costs.  They can leak a caustic potassium hydroxide.  An irritant to your eyes and skin.  As well as your respiratory system.  As they age they can produce hydrogen gas.  Which can rupture the casing.  If a battery leaks potassium carbonate (a crystalline structure) can grow.  If this crystalline structure reaches the copper tracks of a circuit board it will oxidize the copper and metallic components.  Damaging electronic devices.  But the benefits clearly outweigh the risks.  As about 80% of all batteries sold in the U.S. are alkaline batteries.

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Fire, Oil Lamp, Candle, Wicks, Gas Lights, Incandescence, Incandescent Light Bulb, Fluorescence and Compact Fluorescent Lamp

Posted by PITHOCRATES - February 20th, 2013

Technology 101

(Originally published March 28th, 2012)

A Lit Match heats the Fuel Absorbed into a Wick, Vaporizes it, Mixes it with Oxygen and Ignites It

Fire changed the world.  From when Homo erectus first captured it.  Around 600,000 BC.  In China.  They saw it.  Maybe following a lightning strike.  Seeing it around volcanic activity.  Perhaps a burning natural gas vent.  Whatever.  They saw fire.  Approached it.  And learned not to fear it.  How to add fuel to it.  To transfer it to another fuel source.  To carry it.  They couldn’t create fire.  But they could manage it.  And use it.  It was warm.  And bright.  So they brought it indoors.  To light up their caves.  Scare the predators out.  To use it to heat.  And to cook.  Taking a giant leap forward for mankind.

When man moved into man-made dwellings they brought fire with them.  At first a one-room structure with a fire in the center of it.  And a hole in the roof above it.  Where everyone gathered around to eat.  Stay warm.  Sleep.  Even to make babies.  As there wasn’t a lot of modesty back then.  Not that anyone complained much.  What was a little romance next to you when you were living in a room full of smoke, soot and ash?  Fireplaces and chimneys changed all that.  Back to back fireplaces could share a chimney.  Providing more heat and light.  Less smoke and ash.  And a little privacy.  Where the family could be in one room eating, staying warm, reading, playing games and sleeping.  While the grownups could make babies in the other room.

As we advanced so did our literacy.  After a hard day’s work we went inside.  After the sun set.  To read.  Write letters.  Do some paperwork for the business.  Write an opera.  Whatever.  Even during the summer time.  When it was warm.  And we didn’t have a large fire burning in the fireplace.  But we could still see to read and write.  Thanks to candles.  And oil lamps.  One using a liquid fuel.  One using a solid fuel.  But they both operate basically the same.  The wick draws liquid (or liquefied) fuel via capillary action.  Where a porous substance placed into contact with a liquid will absorb that liquid.  Like a paper towel or a sponge.  When you place a lit match into contact with the wick it heats the fuel absorbed into the wick and vaporizes it.  Mixing it with the oxygen in the air.  And ignites it.  Creating a flame.  The candle works the same way only starting with a solid fuel.  The match melts the top of this fuel and liquefies it.  Then it works the same way as an oil lamp.  With the heat of the flame melting the solid fuel to continue the process.

Placing a Mantle over a Flame created Light through Incandescence (when a Heated Object emits Visible Light)

Two popular oils were olive oil and whale oil.  Beeswax and tallow were common solid fuels.  Candles set the standard for noting lighting intensity.  One candle flame produced one candlepower.  Or ‘candela’ as we refer to it now.   (Which equals about 13 lumens – the amount of light emitted by a source).  If you placed multiple candles into a candelabrum you could increase the lighting intensity.  Three candles gave you 3 candela of light to read or write by.  A chandelier with numerous candles suspended from the ceiling could illuminate a room.  This artificial light shortened the nights.  And increased the working day.  In the 19th century John D. Rockefeller gave the world a new fuel for their oil lamps.  Kerosene.  Refined from petroleum oil.  And saved the whales.  By providing a more plentiful fuel.  At cheaper prices.

By shortening the nights we also made our streets safer.  Some cities passed laws for people living on streets to hang a lamp or two outside.  To light up the street.  Which did indeed help make the streets brighter.  And safer.  To improve on this street lighting idea required a new fuel.  Something in a gas form.  Something that you could pump into a piping system and route to the new street lamps.  A gas kept under a slight pressure so that it would flow up the lamp post.  Where you opened the gas spigot at night.  And lit the gas.  And the lamp glowed until you turned off the gas spigot in the morning.  Another advantage of gas lighting was it didn’t need wicks.  Just a nozzle for the gas to come out of where you could light it.  So there was no need to refuel or to replace the wicks.  Thus allowing them to stay lit for long periods with minimum maintenance.  We later put a mantle over the flame.  And used the flame to heat the mantle which then glowed bright white.  A mantle is like a little bag that fits over the flame made out of a heat resistant fabric.  Infused into the fabric are things that glow white when heated.  Rare-earth metallic salts.  Which change into solid oxides when heated to incandescence (when a heated object emits visible light).

One of the first gases we used was coal-gas.  Discovered in coal mines.  And then produced outside of a coal mine from mined coal.  It worked great.  But when it burned it emitted carbon.  Like all these open flames did.  Which is a bit of a drawback for indoor use.  Filling your house up with smoke.  And soot.  Not to mention that other thing.  Filling up your house with open flames.  Which can be very dangerous indoors.  So we enclosed some of these flames.  Placing them in a glass chimney.  Or glass boxes.  As in street lighting.  Enclosing the flame completely (but with enough venting to sustain the flame) to prevent the rain form putting it out.  This glass, though, blackened from all that carbon and soot.  Adding additional maintenance.  But at least they were safer.   And less of a fire hazard.  Well, at least less of one type of fire hazard.  From the flame.  But there was another hazard.  We were piping gas everywhere.  Outside.  Into buildings.  Even into our homes.  Where it wasn’t uncommon for this gas to go boom.  Particularly dangerous were theatres.  Where they turned on the gas.  And then went to each gas nozzle with an open fire on a stick to light them.  And if they didn’t move quickly enough the theatre filled with a lot of gas.  An enclosed space filled with a lot of gas with someone walking around with an open fire on a stick.  Never a good thing.

Fluorescent Lighting is the Lighting of Choice in Commercial, Professional and Institutional Buildings

Thomas Edison fixed all of these problems.  By finding another way to produce incandescence. By running an electrical current through a filament inside a sealed bulb.  The current heated the filament to incandescence.  Creating a lot of heat.  And some visible light.  First filaments were carbon based.  Then tungsten became the filament of choice.  Because they lasted longer.  At first the bulbs contained a vacuum.  But they found later that a noble gas prevented the blackening of the bulb.  The incandescent light bulb ended the era of gas lighting.  For it was safer.  Required less maintenance.  And was much easier to operate.  All you had to do was flick a switch.  As amazing as the incandescent light bulb was it had one big drawback.  Especially when we use a lot of them indoors.  That heat.  As the filament produced far more heat than light.  Which made hot buildings hotter.  And made air conditioners work harder getting that heat out of the building.  Enter the fluorescent lamp.

If phosphor absorbs invisible short-wave ultraviolet radiation it will fluoresce.  And emit long-wave visible light.  But not through incandescence.  But by luminescence.  Instead of using heat to produce light this process uses cooler electromagnetic radiation.  Which forms the basis of the fluorescent lamp.  A gas-discharge lamp.  The most common being the 4-foot tube you see in office buildings.  This tube has an electrode at each end.  Contains a noble gas (outer shell of valence electrons are full and not chemically reactive or electrically conductive) at a low pressure.  And a little bit of mercury.  When we turn on the lamp we create an electric field between the electrodes.  As it grows in intensity it eventually pulls electrons out of their valence shell ionizing the gas into an electrically conductive plasma.  This creates an arc between the electrodes.  This charged plasma field excites the mercury.  Which produces the invisible short-wave ultraviolet radiation that the phosphor absorbs.  Causing fluorescence.

One candle produces about 13 lumens of light.  Barely enough to read and write by.  Whereas a 100W incandescent light bulb produces about 1,600 lumens.  The equivalent of 123 candles.  In other words, one incandescent lamp produces the same amount of light as a 123-candle chandelier.  Without the smoke, soot or fire hazard.  And the compact fluorescent lamp improves on this.  For a 26W compact fluorescent lamp can produce the lumen output of a 100W incandescent light bulb.  A one-to-one tradeoff on lighting output.  At a quarter of the power consumption.  And producing less heat due to creating light from fluorescence instead of incandescence.  Making fluorescent lighting the lighting of choice in commercial, professional and institutional buildings.  And any other air conditioned space with large lighting loads.

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Lead–Acid Battery, Nickel–Cadmium Battery (NiCd), Nickel–Metal Hydride Battery (NiMH) and Lithium-Ion Battery

Posted by PITHOCRATES - January 9th, 2013

Technology 101

The Chemical Reactions in a Zinc-Carbon Battery are One Way

A battery uses chemistry to make electricity.  An electric current is a flow of electrons that can do useful work.  The chemical reaction inside a battery creates that flow of electrons to produce an electric current.  In a common zinc-carbon battery, for example, a zinc electrode dissolves in an electrolyte.  As it does atoms release free electrons and become positive ions (cations) in the electrolyte.  Giving this solution a positive charge.  At the same time a carbon electrode is in a different electrolyte solution.  One filled with negative ions (anions).  Giving this solution a negative charge.

With no electrical load attached to the battery these electrodes and electrolytes are in equilibrium.  When we attach an external circuit across the battery terminals they provide a pathway for those free electrons.  As the free electrons travel through the external circuit the cations and anions travel through a porous membrane from one electrolyte to the other.  The positive cations (atoms with room for an additional electron) flow towards the carbon electrode.  And combine with the free electrons on the surface of the carbon electrode and become electrically neutral.

We can stop this chemical reaction.  Say by turning a flashlight or a portable radio off.  But we can’t reverse it.  This is a one-way chemical reaction that eventually dissolves away the anode.  A Zinc-carbon battery is inexpensive.  The amount of battery life we get out of it more than offsets the price.  And they’re easy to change.  But sometimes an application calls for a battery that isn’t easy to change.  Like a car battery.  Imagine having to change that a few times a year when it ran down.  No, that would be far too inconvenient.  Difficult.  And costly.  So we don’t.  Instead, we recharge car batteries.

The Chemical Reactions in a Lead-Acid Battery are Reversible allowing these batteries to be Recharged

A car battery is a lead-acid battery.  Each cell of a lead-acid battery has a positive electrode (i.e., plate) of lead dioxide.  A negative electrode of lead.  And an electrolyte of a sulfuric acid-water solution containing sulfate ions.  The lead chemically reacts with the sulfate ions to produce lead sulfate on the negative electrode while producing positive ions.  The lead dioxide chemically reacts with the sulfuric acid to produce lead sulfate on the positive electrode while giving up free electrons.

When we attach an external circuit to the battery (such as starting a car) the free electrons leave the positive electrode, travel through the external circuit and return to the battery.  Where they combine with those positive ions.  Lead sulfate forms on both electrodes.  These reactions consume the sulfuric acid in the electrolyte and leave mostly water behind.  Reducing the available charge in the battery.  But unlike zinc-carbon batteries these chemical reactions are reversible.  After a car starts, for example, the alternator provides the electric power needs of the car.  While applying a charging voltage to the battery.  This voltage will ionize the water in the battery which will break down the lead sulfate.  Deposit lead oxide back onto the positive electrode.  And deposit lead back onto the negative electrode.  Giving you a charged battery for the next time you need to start your engine.

A lead acid battery can provide a strong current to spin an internal combustion engine.  Which takes a lot of energy to fight the compression of the pistons.  And it can work in some very cold temperatures.  But it’s big and heavy.  And works best in things bigger and heavier.  Like cars.  Trucks.  Trains.  And ships.  But they don’t work well in things that are smaller and lighter.  Like cordless power tools.  Cell phones.  And laptop computers.  Things where battery weight is an important issue.  Requiring an alternative to the lead-acid battery.  One of the earliest rechargeable battery alternatives was the nickel–cadmium battery.  Or NiCad battery.

The Chemical Reactions produce Heat in a Lithium Ion Battery and can Catch Fire or Explode

The nickel–cadmium battery works like every other battery.  With chemical reactions that produce electrons.  And chemical reactions that consumes electrons.  The NiCad battery uses nickel (III) oxide-hydroxide for the positive electrode.  Cadmium for the negative electrode.  And potassium hydroxide as the electrolyte.  A NiCad battery may look like a zinc-carbon battery.  But the electrodes are different.  Instead of the zinc canister and a carbon rod the electrodes in a NiCad battery are long strips.  One is placed onto the other with a separator in between.  Then rolled up like a jelly-roll.

NiCad batteries have a memory effect.  If they were recharged without being fully discharged the battery ‘remembers’ the amount of charge it took to recharge the partially discharged battery.  So even if you fully discharged the battery it would only recharge it as if you partially discharged it.  Reducing the battery capacity over time.  The nickel–metal hydride battery (NiMH) eliminated this problem.  And improved on the NiCad.  Giving it 2-3 times the capacity of a NiCad battery.  NiCad and NiMH batteries are very similar.  They use the same positive electrode.  But instead of the highly toxic cadmium NiMH batteries use a mixture of a rare earth metal mixed with another metal.

Today battery technology has evolved into the lithium-ion battery.  Where the positive electrode is a compound containing lithium.  The negative electrode is typically graphite.  The electrolyte is a lithium salt.  Lithium ions travel between the electrodes through the electrolyte.  And electrons flow between the electrodes via the external circuit.  They have a greater capacity, no memory effect and hold their charge for a long time when not being used.  Making the lithium ion battery ideal for cell phones and other consumer electronics.  These chemical reactions produce heat, though.  And can catch fire or explode.  Trying to prevent this from happening increases their manufacturing costs, making them expensive batteries.  So expensive that people will buy cheaper generic brands.  Cheaper because they are not built to the same quality standards of the more expensive ones.  And are more prone to catching fire or exploding.

Something to think about when you feel the heat of your cell phone after a long conversation.  Only use a battery recommended by the manufacturer.  Even if it costs a small fortune.  It may be expensive.  But probably not as expensive as your monthly airtime charges.  So don’t skimp when it comes to lithium ion batteries.  For those cheap ones do have a tendency to catch fire.  Or explode.

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Leyden Jar, Electric Charge, Galvanic Cell, Voltaic Pile, Anions, Cations, Daniell Cell, Zinc-Carbon Battery and Alkaline Battery

Posted by PITHOCRATES - December 19th, 2012

Technology 101

Luigi Galvani made a Dead Frog’s Leg Twitch when he hit it with the Electric Discharge Shock from a Leyden Jar

The field of electricity took off with friction generators.  Dragging something across another substance to produce an electrical charge.  Like sliding out of your car on a dry winter day.  Producing an electric discharge shock just before your hand touches the metal door to close it.  Atoms in materials are electrically neutral.  There are an equal number of positive particles (protons) and negative particles (electrons).  Friction can transfer some of those electrons from one surface to another.  Leaving one surface with a net positive charge.  And the other with a net negative charge.  These charges equalize after that electric discharge shock.  Returning the atoms in these materials to an electrically neutral state.

Further exploration of static electric charge led to the development of the Leyden jar.  A precursor to the modern capacitor.  A glass jar with metal foil on the inside and outside of a glass bottle.  The foil sheets act as plates.  The glass as a dielectric.  An electrode attached to one plate received an electric charge from a friction generator.  The other plate was grounded.  The dielectric helped the plates hold an electric charge.  Benjamin Franklin did a lot of experiments with the Leyden jar.  He noted how multiple Leyden jars could hold a greater charge.  Commenting that it was like a battery of cannons.  Giving us the word battery for an electrical storage device.

Luigi Galvani made a dead frog’s leg twitch when he zapped it with the electric discharge shock from a Leyden jar.  Furthering his experiments Galvani found that he could reproduce the twitching by placing the frog’s leg between two different types of metals.  Creating a galvanic cell.  Which created an electric current.  Alessandro Volta recreated this experiment while substituting the frog tissue with cardboard soaked in salt water (an electrolyte).  Creating the voltaic cell.  Piling one voltaic cell onto another created a Voltaic Pile.  Or as we call it today, a battery.

A Daniell Cell created a Current by Stripping away Electrons from one Electrode and Recombining them on Another

What Galvani and Volta discovered was a chemical reaction that caused an electric current.  The Voltaic Pile, though, had a limited life.  To improve on it John F. Daniell added a second electrolyte.  Creating the Daniell Cell.  Which extended the life of a battery charge.  Allowing it to do useful work.  Becoming the first commercially successful battery.  Powering our first telegraphs and telephones.  Even finding their way into our homes operating our doorbells for a century or so before Nikola Tesla brought alternating current electric power to our homes.

The chemical reaction in a Daniell Cell created an electric current by stripping away electrons from one metal electrode in a solution (anode oxidation).  And recombining electrons onto another electrode of a different metal in a different solution (cathode reduction).  Each electrode is in an electrolyte solution.  In a copper-zinc Daniell Cell the anode is typically in a solution of zinc sulfate.  And the cathode is in a copper sulfate solution.  A salt bridge or porous membrane connects the different electrolytes.  When an electric load is connected across the ‘battery’ electrodes it completes the electrochemical system.

Each electrolyte contains ions.  Atoms with a net positive or negative charge.  Positive ions are cations.  Negative ions are anions.  The cathode attracts cations.  Where they combine with free electrons to return to a neutral state.  The anode attracts anions.   Where they give up their extra electrons to return to a neutral state.  This chemical activity dissolves the zinc electrode.  And deposits copper on the copper electrode.  (This electrolysis is the basis for the metal plating industry.)  It is the dissolving of the anode that gives up electrons that travel from one electrode through the electric load to the other electrode.  Doing work for us.  By lighting our flashlights.  Or powering our portable radio.  When the anode dissolves to the point that it cannot give up anymore electrons the chemical reaction stops.  And we have to replace our batteries.

An Alkaline Battery will produce more Useable Power and have a longer Shelf Life than a Zinc-Carbon Battery

Of course, the zinc-carbon batteries we use for our flashlights and radios are not wet cells.  They’re dry cells.  Instead of an electrolyte solution the common battery is made up of dry components.  The zinc anode is the battery casing.  Just inside the battery zinc casing is a paper layer impregnated with a moist paste of acidic ammonium chloride.  This separates the zinc can from a mixture of graphite powder and manganese (IV) oxide (pyrolusite).  In the center of the battery is a carbon rod.  The zinc casing is the negative electrode (anode) and the carbon rod is the positive electrode (the cathode).  The chemical reactions are the same as they are with the wet cell.  The zinc casing (the anode) becomes thinner over time.  When holes begin to appear the battery will leak creating a sticky mess.  As you no doubt experienced when taking an old set of batteries out of a flashlight that hasn’t been used in years.

An alkaline battery looks similar to a zinc-carbon battery.  But there are many differences.  Instead of an acidic ammonium chloride electrolyte an alkaline battery uses an alkaline potassium hydroxide electrolyte.  The little nub (positive terminal) on top of the battery does not connect to a carbon rod in the center of the battery.  It connects to the outer casing.  Inside this casing is a mixture of graphite powder and manganese (IV) oxide (pyrolusite).  Then a barrier to keep the anode and cathode materials from coming into contact with each other.  But lets ions pass through.  On the other side of the barrier is the anode.  A gel of the alkaline potassium hydroxide electrolyte containing a dispersion of zinc powder.  In the middle of the battery is a metal rod that acts as a current pickup that connects to the bottom of the battery (the negative terminal).

Alkaline batteries are the most popular batteries today.  Because they have a higher energy density than a zinc-carbon battery.  Meaning that an alkaline battery will produce more useable power than a comparable sized zinc-carbon battery.  And they have a longer shelf life.  But with these benefits comes costs.  They can leak a caustic potassium hydroxide.  An irritant to your eyes and skin.  As well as your respiratory system.  As they age they can produce hydrogen gas.  Which can rupture the casing.  If a battery leaks potassium carbonate (a crystalline structure) can grow.  If this crystalline structure reaches the copper tracks of a circuit board it will oxidize the copper and metallic components.  Damaging electronic devices.  But the benefits clearly outweigh the risks.  As about 80% of all batteries sold in the U.S. are alkaline batteries.

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Fire, Oil Lamp, Candle, Wicks, Gas Lights, Incandescence, Incandescent Light Bulb, Fluorescence and Compact Fluorescent Lamp

Posted by PITHOCRATES - March 28th, 2012

Technology 101

A Lit Match heats the Fuel Absorbed into a Wick, Vaporizes it, Mixes it with Oxygen and Ignites It 

Fire changed the world.  From when Homo erectus first captured it.  Around 600,000 BC.  In China.  They saw it.  Maybe following a lightning strike.  Seeing it around volcanic activity.  Perhaps a burning natural gas vent.  Whatever.  They saw fire.  Approached it.  And learned not to fear it.  How to add fuel to it.  To transfer it to another fuel source.  To carry it.  They couldn’t create fire.  But they could manage it.  And use it.  It was warm.  And bright.  So they brought it indoors.  To light up their caves.  Scare the predators out.  To use it to heat.  And to cook.  Taking a giant leap forward for mankind.

When man moved into man-made dwellings they brought fire with them.  At first a one-room structure with a fire in the center of it.  And a hole in the roof above it.  Where everyone gathered around to eat.  Stay warm.  Sleep.  Even to make babies.  As there wasn’t a lot of modesty back then.  Not that anyone complained much.  What was a little romance next to you when you were living in a room full of smoke, soot and ash?  Fireplaces and chimneys changed all that.  Back to back fireplaces could share a chimney.  Providing more heat and light.  Less smoke and ash.  And a little privacy.  Where the family could be in one room eating, staying warm, reading, playing games and sleeping.  While the grownups could make babies in the other room.

As we advanced so did our literacy.  After a hard day’s work we went inside.  After the sun set.  To read.  Write letters.  Do some paperwork for the business.  Write an opera.  Whatever.  Even during the summer time.  When it was warm.  And we didn’t have a large fire burning in the fireplace.  But we could still see to read and write.  Thanks to candles.  And oil lamps.  One using a liquid fuel.  One using a solid fuel.  But they both operate basically the same.  The wick draws liquid (or liquefied) fuel via capillary action.  Where a porous substance placed into contact with a liquid will absorb that liquid.  Like a paper towel or a sponge.  When you place a lit match into contact with the wick it heats the fuel absorbed into the wick and vaporizes it.  Mixing it with the oxygen in the air.  And ignites it.  Creating a flame.  The candle works the same way only starting with a solid fuel.  The match melts the top of this fuel and liquefies it.  Then it works the same way as an oil lamp.  With the heat of the flame melting the solid fuel to continue the process. 

Placing a Mantle over a Flame created Light through Incandescence (when a Heated Object emits Visible Light)

Two popular oils were olive oil and whale oil.  Beeswax and tallow were common solid fuels.  Candles set the standard for noting lighting intensity.  One candle flame produced one candlepower.  Or ‘candela’ as we refer to it now.   (Which equals about 13 lumens – the amount of light emitted by a source).  If you placed multiple candles into a candelabrum you could increase the lighting intensity.  Three candles gave you 3 candela of light to read or write by.  A chandelier with numerous candles suspended from the ceiling could illuminate a room.  This artificial light shortened the nights.  And increased the working day.  In the 19th century John D. Rockefeller gave the world a new fuel for their oil lamps.  Kerosene.  Refined from petroleum oil.  And saved the whales.  By providing a more plentiful fuel.  At cheaper prices.

By shortening the nights we also made our streets safer.  Some cities passed laws for people living on streets to hang a lamp or two outside.  To light up the street.  Which did indeed help make the streets brighter.  And safer.  To improve on this street lighting idea required a new fuel.  Something in a gas form.  Something that you could pump into a piping system and route to the new street lamps.  A gas kept under a slight pressure so that it would flow up the lamp post.  Where you opened the gas spigot at night.  And lit the gas.  And the lamp glowed until you turned off the gas spigot in the morning.  Another advantage of gas lighting was it didn’t need wicks.  Just a nozzle for the gas to come out of where you could light it.  So there was no need to refuel or to replace the wicks.  Thus allowing them to stay lit for long periods with minimum maintenance.  We later put a mantle over the flame.  And used the flame to heat the mantle which then glowed bright white.  A mantle is like a little bag that fits over the flame made out of a heat resistant fabric.  Infused into the fabric are things that glow white when heated.  Rare-earth metallic salts.  Which change into solid oxides when heated to incandescence (when a heated object emits visible light).

One of the first gases we used was coal-gas.  Discovered in coal mines.  And then produced outside of a coal mine from mined coal.  It worked great.  But when it burned it emitted carbon.  Like all these open flames did.  Which is a bit of a drawback for indoor use.  Filling your house up with smoke.  And soot.  Not to mention that other thing.  Filling up your house with open flames.  Which can be very dangerous indoors.  So we enclosed some of these flames.  Placing them in a glass chimney.  Or glass boxes.  As in street lighting.  Enclosing the flame completely (but with enough venting to sustain the flame) to prevent the rain form putting it out.  This glass, though, blackened from all that carbon and soot.  Adding additional maintenance.  But at least they were safer.   And less of a fire hazard.  Well, at least less of one type of fire hazard.  From the flame.  But there was another hazard.  We were piping gas everywhere.  Outside.  Into buildings.  Even into our homes.  Where it wasn’t uncommon for this gas to go boom.  Particularly dangerous were theatres.  Where they turned on the gas.  And then went to each gas nozzle with an open fire on a stick to light them.  And if they didn’t move quickly enough the theatre filled with a lot of gas.  An enclosed space filled with a lot of gas with someone walking around with an open fire on a stick.  Never a good thing.

Fluorescent Lighting is the Lighting of Choice in Commercial, Professional and Institutional Buildings 

Thomas Edison fixed all of these problems.  By finding another way to produce incandescence. By running an electrical current through a filament inside a sealed bulb.  The current heated the filament to incandescence.  Creating a lot of heat.  And some visible light.  First filaments were carbon based.  Then tungsten became the filament of choice.  Because they lasted longer.  At first the bulbs contained a vacuum.  But they found later that a noble gas prevented the blackening of the bulb.  The incandescent light bulb ended the era of gas lighting.  For it was safer.  Required less maintenance.  And was much easier to operate.  All you had to do was flick a switch.  As amazing as the incandescent light bulb was it had one big drawback.  Especially when we use a lot of them indoors.  That heat.  As the filament produced far more heat than light.  Which made hot buildings hotter.  And made air conditioners work harder getting that heat out of the building.  Enter the fluorescent lamp.

If phosphor absorbs invisible short-wave ultraviolet radiation it will fluoresce.  And emit long-wave visible light.  But not through incandescence.  But by luminescence.  Instead of using heat to produce light this process uses cooler electromagnetic radiation.  Which forms the basis of the fluorescent lamp.  A gas-discharge lamp.  The most common being the 4-foot tube you see in office buildings.  This tube has an electrode at each end.  Contains a noble gas (outer shell of valence electrons are full and not chemically reactive or electrically conductive) at a low pressure.  And a little bit of mercury.  When we turn on the lamp we create an electric field between the electrodes.  As it grows in intensity it eventually pulls electrons out of their valence shell ionizing the gas into an electrically conductive plasma.  This creates an arc between the electrodes.  This charged plasma field excites the mercury.  Which produces the invisible short-wave ultraviolet radiation that the phosphor absorbs.  Causing fluorescence.

One candle produces about 13 lumens of light.  Barely enough to read and write by.  Whereas a 100W incandescent light bulb produces about 1,600 lumens.  The equivalent of 123 candles.  In other words, one incandescent lamp produces the same amount of light as a 123-candle chandelier.  Without the smoke, soot or fire hazard.  And the compact fluorescent lamp improves on this.  For a 26W compact fluorescent lamp can produce the lumen output of a 100W incandescent light bulb.  A one-to-one tradeoff on lighting output.  At a quarter of the power consumption.  And producing less heat due to creating light from fluorescence instead of incandescence.  Making fluorescent lighting the lighting of choice in commercial, professional and institutional buildings.  And any other air conditioned space with large lighting loads. 

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