Please select a subject first
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Which of the following statements are correct?
- Sound is produced by vibrations.
- Sound requires a medium for propagation.
- Light and sound both require a medium for propagation.
- Sound travels slower than light.
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Lightning can be seen the moment it occurs. Paheli observes lightning in her area. She hears the sound 5 s after she observed lightning. How far is she from the place where lightning occurs? (speed of sound = 330 m/s).
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Name two musical instruments which produce sound by vibrating strings.
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Electric current is to be passed from one body to another. For this purpose, the two bodies must be joined by
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During the construction of a building, the lightning conductor was left hanging in the air by mistake. Would the lightning conductor be still effective? Explain.
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If air and cloud were good conductors of electricity, do you think lightning could occur? Explain.
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Identify the lightning conductor and the copper plate in the following figure.
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If the materials used for constructing a building were good conductors, do you think lightning will strike the building. Will the lightning conductor be still required to be installed in the building?
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You might have observed on a dry day that when you touch the screen of a television or computer monitor (with picture tube), you get a slight shock. Why does it happen?
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Explain how does lightning conductor protects a building from getting struck by lightning.
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Explain how lightning takes place.
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Explain why it is safer to use a wireless telephone instead of a landline telephone during lightning.
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What precautions would you take if lightning occurs while you are outside the house?
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What happens to light when it gets dispersed? Give an example.
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Burning of wood and coal causes ______ of air.
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Fire produced by oil cannot be controlled by ______.
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Give reasons.
Water is not used to control fires involving electrical equipment.
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Explain how CO2 is able to control fires.
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It is difficult to burn a heap of green leaves but dry leaves catch fire easily. Explain
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Which zone of a flame does a goldsmith use for melting gold and silver and why?
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