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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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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Sound Waves, Phonograph, Stylus, Piezoelectric & Magnetic Cartridges, Thermionic Emission, Vacuum Tube, PN-Junction, Transistor and Amplifier

Posted by PITHOCRATES - May 2nd, 2012

Technology 101

The First Phonographs used a Stylus attached to a Diaphragm to Vibrate the Air and a Horn for Amplification 

Sound is vibration.  Sound waves we hear are vibrations in the air.  A plucked guitar string vibrates.  It transfers that vibration to the soundboard on the guitar body.  The vibration of the soundboard vibrates the air inside the guitar body.  Amplifying it.  And shaping it.  Giving it a rich and resonant sound.  Creating music.  And we can reverse this process.  Taking these vibrations from the air.  And putting them into a piece of wax.  Via a vibrating needle.  Or stylus.  Cutting wavy grooves into wax.  And then we can even reverse this process.  By dragging a stylus through those same wavy groves.  Causing the stylus to vibrate.  And if we transfer those vibrations to the air we can hear those sound waves.  And listen to the music they make.

The first phonographs could reproduce sound.  But they didn’t sound very good.  The first phonographs were purely mechanical.  A stylus vibrated a diaphragm.  The diaphragm vibrated the air.  And a horn attached to that diaphragm was the only amplification.  Sort of like cupping your hands around your mouth when shouting.  Which reinforced and concentrated the sound waves.  Making them louder in the direction you were facing.  Which is how these early phonographs worked.  But the quality of the sound was terrible.  And played at only one volume.  Low.

Electric circuits changed the way we listen to music.  Because we could amplify those low volumes.  By changing the vibrations created from those wavy grooves into an electrical signal.  The first phonographs used a piezoelectric cartridge.  Which the stylus attached to.  The piezoelectric cartridge converted a mechanical pressure (the needle vibrating in the wavy groove) into electricity.  Later phonographs used a magnetic cartridge.  Which did the same thing only using a varying magnetic field.  The vibration of the needle moved a magnet or a coil through a magnetic field.  Thus inducing a current in a coil.  Then all you needed was an amplifier and a loudspeaker to make sweet music.

Small Changes in the Control Grid Voltage of a Vacuum Tube make Larger Changes in the Plate Voltage

The first amplifiers used vacuum tubes.  Things that once filled our televisions and stereo systems.  Back in the old days.  Up until about the Seventies.  A vacuum tube operated on the principle of thermionic emission.  Which basically means if you heat a metal filament it will ‘boil off’ electrons.  The basic vacuum tube used for amplification consisted of a cathode and an anode.  Or filament and plate.  And a control grid in between.  Sealed in, of course, a vacuum.  Creating the triode.  The cathode (filament) and anode (plate) created an electric field when connected to a large power source.  The cathode is negative.  And the anode is positive.  When negatively charged electrons are ‘boiled off’ of the cathode the positive anode attracts them.  The greater the heat the greater the thermionic emission.  And the greater the current flow from cathode to anode.  Unless we change the electric field to inhibit the flow of current.  Which is the purpose of the control grid.

Small changes in the control grid voltage will make changes in the large current flowing from cathode to anode.  That is, the larger current replicates the smaller signal applied to the control grid.  This allows the triode to take the low voltage from a phonograph cartridge and amplify it to a higher voltage with enough power to drive a loudspeaker.  Which is similar to diaphragm and horn on the first phonographs.  Only the amplified electric signal moves a lot more air.  And better materials and construction create a better quality sound.  Amplifiers with vacuum tubes make beautiful music.  High-end audio equipment still uses them to this day.  Including almost all electric guitar amps.  So if they have the highest quality why don’t we use them elsewhere?  Because of thermionic emission.  And the heat required to ‘boil off’ those electrons.

Vacuum tubes worked well when plugged into line power.  Such as a radio in a house.  But they don’t work well on batteries.  Because it takes a lot of electric power to heat those filaments.  And you need pretty big batteries to get that kind of electric power.  Like a car battery.  But even a car battery didn’t let you listen to music for long when parked with the engine off.  Because those tubes drained that battery pretty fast.  So there were limitations in using vacuum tubes.  They draw a lot of power.  Produce a lot of heat.  And tend to be pieces of furniture in your house because of their physical size.

Small Changes in the Base Current of a Transistor is Replicated in the Larger Collector-Emitter Current

The transistor changed that.  Making music more portable.  Thanks to semiconductors.  Material with special electric properties.  Based on the amount of electrons in the atoms making up this material.  Atoms with extra electrons make material with a negative charge (N-material).  Atoms missing some electrons make material with a positive charge (P-material).  When you put these materials together the N and the P attract each other.  Electrons cross the junction and fill in the holes that were missing electrons.  And the ‘holes’ cross the junction and fill in the spaces where there were excess electrons.  (When an electron moved, say, from right to left it made a hole and filled a hole.  It made a hole where it once was.  And it filled a hole where it now is.  So it looks like the hole moved from left to right when the electron moved from right to left.)  Neutralizing the N-material and the P-material.  But creating a charged region around the junction.  And it’s this electron flow and hole flow that make these PN junctions work.  When you add a third material you get a transistor.  Made up of three parts (NPN or PNP).  Emitter, base, and collector.

To get the electrons and holes flowing you start applying voltages across the junctions.  A large current will flow from the collector to the emitter.  Similar to the current flow in a tube from cathode to anode.  And a small base current will change that current flow.  Just like the control grid in a vacuum tube.  Small changes in the base current will make similar changes in the larger collector-emitter current.  Just like in a vacuum tube, the larger current replicates the smaller signal applied to the ‘control’.  Or base.  This allows the transistor to take the low-level signal from a phonograph cartridge and amplify it to a higher level.  Just like a vacuum tube.  Only with a fraction of the electric power.  Because there are no filaments to heat. 

Low power consumption and the small physical size allowed much smaller amplifiers.  And amplifiers that everyday batteries could power.  Creating new ways to listen to music.  From the pocket-size transistor radio.  To the bigger stereo boombox.  To the iPod.  Where the basic principle of how we listen to music hasn’t changed.  Just how we vibrate the air that makes that music has.

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