Assertion (A) : The temperature of a metal wire rises when an electric current is passed through it. Reason (R) : Collision of metal atoms with each other releases heat energy.

Assertion is true: when current flows through a metal wire some electrical energy is dissipated as heat due to the wire’s resistance, so the wire’s temperature rises (observed for nichrome and other conductors) [1]. Reason is false as stated: heat is not produced by collisions of metal atoms with each other. Microscopically, moving conduction electrons scatter from the vibrating lattice ions (and impurities), transferring energy to the lattice and increasing ionic vibrational energy — i.e., temperature rises due to electron–lattice (electron–ion) collisions, not atom–atom collisions. This electron–lattice energy transfer underlies Joule heating and the P = I^2R heating behavior.

Sources

1. [1] Science ,Class VIII . NCERT(Revised ed 2025) > Chapter 4: Electricity: Magnetic and Heating Effects > Activity 4.5: Let us observe > p. 53