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...a Conductor
The use of silver as a link, a conductor of heat and electricity without
creating sparks is one of the metal's most valuable industrial applications.
Silver has the highest thermal and electrical conductivity of any metal.
According to the Silver
Institute:
Silver is the best electrical conductor of all metals and
is hence used in many electrical applications, particularly in conductors,
switches, contacts and fuses. Contacts, a junction between two conductors
that can be separated and through which a current can flow, account
for the largest proportion of electrical demand...
Over 50 categories of electrical components incorporating silver as
the contact material are listed by The National Electrical Manufacturers
Association, Washington, D.C. These range from silver thick films
that are used to make membrane switches which carry 5 volts or less
for electronic systems, to large circuit breaker contacts required
to interrupt or close the circuits of 75,000-volt power distribution
lines.
The use of silver for motor control switches is universal. In the
home, wall switches, timing devices, thermostats, sump pumps, and
virtually all electrical appliances use silver contacts. A typical
washing machine requires 16 silver contacts to control its electric
motor, pump, and gear clutch. A fully-equipped automobile may have
over 40 silver-tipped switches to start the engine, activate power
steering, brakes, windows, mirrors, locks, and other electrical accessories.
Relays are another important market for silver contacts. Relays are
used when low voltage switches (such as membrane switches) are used
to activate considerably higher voltage or amperage switches. The
increasing use of automated appliances has increased the number of
silver contacts manufactured in the US.
Electric motor control switches use the largest amount of silver for
each contact. The range of applications is enormous, covering: washing
machines, dryers, automobile accessories, vacuum cleaners, electric
drills, elevators, escalators, machine tools, and so on up to railway
locomotives and marine diesel engines. Silver contacts start motors,
set them to run forward or reverse, or at partial or full power. The
silver contacts carry electrical power ranging from a fraction of
an ampere, for small appliances, to 600-ampere loads required for
oil-well drilling motors; their performance is required to be flawless.
Nearly half of the 20 million troy ounces of silver consumed in the
USA yearly for contacts and conductors is used for motor controls.
The circuit breaker is the second major user of silver for contacts.
For circuit breakers, silver combines the highest heat conductivity
and the highest electrical conductivity of all metals, with almost
unlimited performance. Circuit breakers are used to interrupt loads
ranging from 10 amperes (small household lines) to 4000 amperes (high-tension
power lines).
The circuit breaker is the most demanding use of silver contacts because
the temperature of the arc generated by the interruption of high electrical
power often exceeds the melting point of silver. As a consequence, silver
is alloyed or infiltrated into other metals such as Tungsten to provide
long-term performance.
Silver's conductivity is also used in electronics:
including keyboards, TV's, microwaves, and washing machines.
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