Page:Electricity (1912) Kapp.djvu/133

Rh tin are used for the fuse wire, this must be much stouter than would be the case with copper or silver; consequently the amount of material, which by the heating is volatilised, becomes so great that the process resembles rather an explosion than a quiet melting, and the envelope may be shattered, letting out the flash, and thus the fuse itself may become a source of danger. In this respect the best material for fuse wires is silver. An exceedingly thin silver wire will carry a fairly large current, and if the current should rise to a dangerous value and the wire be fused, the amount of material volatilised is so small that there is hardly any explosive effect, especially if the wire is embedded in carborundum powder.

Now the reader may ask, why should a thin silver wire suffice if for the same current a stout lead wire is necessary? This comes from the physical fact that silver is far better adapted than lead for carrying an electric current, it conducts better, or, as we also may say, it has a higher "conductivity." By this we mean that to get the current through the wire the force which is pushing the electricity from one end to the other is much smaller with silver than with lead; silver offers less "resistance" to the flow of electricity than lead.