Which of the following materials is typically used for main bonding jumpers in electrical systems?

The use of copper for main bonding jumpers in electrical systems is primarily due to its excellent electrical conductivity and resistance to corrosion. Copper provides a reliable and effective path for fault currents, helping to ensure safety by facilitating the operation of protective devices in the event of a fault. The material's ductility allows for easy handling and installation, which is beneficial in various electrical applications.

While aluminum is another conductive material, it generally has higher resistance than copper and can be more difficult to work with regarding reliable connections. Steel, though it is magnetic and stronger structurally, does not provide adequate conductivity compared to copper and is more prone to corrosion. Gold, while an excellent conductor, is cost-prohibitive and not practical for use in bonding jumpers where extensive lengths and connections may be required. Thus, copper remains the preferred choice due to its balance of efficiency, safety, and practicality in electrical systems.