Soldering other precipitation may wash the lead into the groundwater. Unfortunately, most lead-free solders are not eutectic formulations, melting at around , making it more difficult to create reliable joints with them. Other common solders include low-temperature formulations (often containing bismuth), which are often used to join previously-soldered assemblies without unsoldering earlier connections, and high-temperature formulations (usually containing silver) which are used for high-temperature operation or for first assembly of items which must not become unsoldered during subsequent operations. Alloying silver with other metals changes the melting point, adhesion and wetting characteristics, and tensile strength. Of all the brazing alloys, silver
Electrical length of "(2N+1)λ"/2. The electrical length of an antenna element is, in general, different from its physical length For example, increasing the diameter of the conductor, or the presence of nearby metal objects, will decrease the velocity of the waves in the element, increasing the electrical length. An antenna which is shorter than its resonant length is described as ""electrically short"" , and exhibits capacitive reactance. Similarly, an antenna which is longer than its resonant length is described as ""electrically long"" and exhibits inductive reactance. An antenna's effective electrical length can be changed without changing its physical length by adding reactance,