Question

The gap kept between rail lengths on railway tracks is based on the phenomenon of 
1. seismic waves
2. thermal expansion
3. shift of tectonic plates
4. all of the above

Answer 1

Correct Answer - Option 2 : thermal expansion

The correct answer is option 2) i.e. thermal expansion

CONCEPT:

• Thermal expansion: Thermal expansion is the tendency of objects to undergo a change in shape, volume, and area due to a change in their temperature.
  • In general, substances expand on heating and contract on cooling.
  • On heating, the average kinetic energy of the molecules increases and they start moving vigorously about their mean position.
  • In the process, the intermolecular spacing increases and the material expands in all directions.

EXPLANATION:

• The rails are generally made of metals.
• The gap between the rails provides a space for the metal to expand during the summer and contract during the winter season.
• Therefore, the gaps between rail lengths are to accommodate the expansion and contraction of metal due to thermal expansion.