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प्रश्न
Why do telephone wires sag in summer ?
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उत्तर
The telephone wires will sag in summer due to expansions and will break in winter due to contraction.
Therefore, while putting up the wires between the poles, care is taken that in summer they are kept slightly loose so that they may not break in winter due to contraction.
While in winter they are kept light so that they may not sag too much in summer due to expansion.
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संबंधित प्रश्न
Write true or false for a given statement.
Equal volumes of different liquids expand by different amounts when they are heated to the same rise in temperature.
Fill in the blank
Still air is an __________ of heat.
Iron rims are heated before they are fixed on the wooden wheels. Explain the reason.
One end of a steel girder in a bridge is not fixed, but is kept on roliers. Give the reason.
What are the good and bad conductors of heat ? Give two examples of each.
Select good and bad conductors of heat from the following:
copper, mercury, wood, iron, air, saw-dust, cardboard, silver, plastic, wool.
In summer, ice is kept wrapped in a gunny bag. Explain the reason.
In ice cubes, the force of attraction between the water molecules is ______.
Match the following
| 1. | Solid to liquid | a. | Condensation |
| 2. | Liquid to gas | b. | Deposition |
| 3. | Gas to solid | c. | Melting |
| 4. | Gas to liquid | d. | Vaporization |
Mention the factors affecting the flow of heat.
