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Old 01-23-2012, 12:22 AM   #11 (permalink)
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Originally Posted by Blue Bomber View Post
To get a better spark, you need to use a good conductor. Copper is one of the best conductors available for spark plugs
Sorry, but I came across this in a Google search and it is complete nonsense. The resistivities are Platinum = 1.0610^−7 Ωm vs Copper = 1.6810^−8 Ωm.

The total resistance of the copper/platinum/iridium conductor is maybe billionths of an ohm. Meanwhile, it's in series with the spark plug wires, which typically have a resistance of 10,000 to 15,000 ohms. So you're talking about a difference between 10000.000000001 ohms and 10000.000000006 ohms. The difference between the conductivity of copper and platinum is totally irrelevant, and couldn't even be measured.

Platinum is used because it's more durable, not because it's a better conductor. (Same for gold-plated audio cable connectors, incidentally.) This allows it to be made into a narrower electrode without eroding away as quickly as copper would, to make it sharper (higher electric field strength = easier to arc), and to absorb less heat.

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