If the electrical resistance of a typical substance suddenly drops to zero, then the substance is called :

A substance whose electrical resistance suddenly drops to zero is called a superconductor. While normal conductors like copper and aluminum have low resistivity, they still possess finite resistance that causes energy loss as heat [c4, t4]. In contrast, superconductivity is a property where certain materials, when cooled below a specific critical temperature (Tc), exhibit absolutely zero electrical resistance [t1, t5]. This phenomenon allows direct current to flow indefinitely without any energy loss [t1, t9]. Unlike semiconductors, which have intermediate conductivity between insulators and conductors [t2, t10], or insulators that offer extremely high resistance [c2], superconductors allow for the unlimited flow of current once the threshold temperature is reached [t2, t3]. This abrupt drop to zero resistance distinguishes superconductors from normal conductors, whose resistance merely decreases slowly with temperature but remains finite even near absolute zero [t4, t9].

Sources

1. [1] https://www.energy.gov/science/doe-explainssuperconductivity
2. [2] Science , class X (NCERT 2025 ed.) > Chapter 11: Electricity > Figure 11.4 > p. 177
3. [3] Science , class X (NCERT 2025 ed.) > Chapter 11: Electricity > Activity 11.3 > p. 179