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 element defined by a relation between the state variables of the network: current, formula_1; voltage, formula_2, charge, formula_3; and magnetic flux, formula_4. In reality, all circuit components are non-linear and can only be approximated to linear over a certain range. To more exactly describe the passive elements, their constitutive relation is used instead of simple proportionality. From any two of the circuit variables there are six constitutive relations that can be formed. From this it is supposed that there is a theoretical fourth passive element since there are only five elements in total (not including the various dependent sources) found in