UPSC Prelims 1998·GS1·science-and-technology·science and technology

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.

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  1. ABoth A and R are true, and R is the correct explanation of A
  2. BBoth A and R are true, but R is NOT a correct explanation of A
  3. CA is true, but R is falseCorrect
  4. DA is false, but R is true

Explanation

The assertion is true because when an electric current passes through a metal wire, it encounters resistance, which converts electrical energy into heat energy. This is known as the Joule heating effect. The reason is false because the heat is not generated by the collision of metal atoms with each other. In a solid metal lattice, the atoms are fixed in position and do not collide. Instead, the heat is generated by the collisions between the moving free electrons and the stationary metal ions or atoms. These collisions transfer kinetic energy to the lattice, causing the atoms to vibrate more vigorously and increasing the temperature of the wire. Therefore, assertion A is true but reason R is false.
science-and-technology: Assertion (A): The temperature of a metal wire rises when an electric current is passed through it. Reason (R): Collisio
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