MCQ Detailed View

Railway tracks are made of long steel rails that are laid end to end. If these rails were placed tightly without any gaps, serious safety problems could occur when temperatures change throughout the year. The main reason for leaving small gaps between two rails is to avoid accidents due to thermal expansion in summer.

Metals like steel expand when they are heated and contract when they are cooled. This property is known as thermal expansion. During hot summer days, the temperature of the steel rails increases significantly. As the rails expand, they need extra space to stretch. If no gap were left, the expanding metal would push against adjacent rails, causing the track to buckle or bend. Such deformation could lead to derailments and accidents.

In winter, rails contract slightly, but this contraction does not cause major problems because the gap size is calculated carefully by engineers. The primary concern is expansion during high heat, which is much larger than contraction in the cold. Therefore, leaving controlled gaps allows rails to expand safely without damaging the track.

Other options given in the question are incorrect:

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  Steel can be saved: The purpose of the gap is not to reduce material usage.

  
  


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  Accidents due to contraction in winter: Contraction does not create serious safety hazards.

  
  


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  Air gaps to bear train weight: Gaps have nothing to do with weight-bearing strength.

  
  


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  All of these: Only thermal expansion is the correct reason.

  
  

This concept belongs to Physics, under the topic thermal properties of solids. It demonstrates how materials respond to temperature changes and why engineers must account for thermal expansion when constructing bridges, pipelines, and railway tracks.