A lightweight composite electrical wire having a fusible core encased or enclosed by a conductive wall. In embodiments the core is sodium, and the wall is aluminum. In another embodiment the wall is a curved bimetallic wall having a first wall component having a high CTE and a second wall component having a low CTE such that changes in temperature will generate stresses that tend to change the shape of the wall, wherein a break in a heated wire will cause retraction of the core. Transverse bulkheads separate the core longitudinally, precluding or mitigating any loss of core material in accident scenarios, and providing locations for cutting and connecting the conductor. The bulkheads may include indentations. A insulative outer layer is provided. A novel outer layer construction utilizes fusible materials to provide insulation in accident scenarios.