Secondary School (English Medium) (5 to 8) कक्षा ८ - CBSE Question Bank Solutions

Which of the following statements are correct?

1. Sound is produced by vibrations.
2. Sound requires a medium for propagation.
3. Light and sound both require a medium for propagation.
4. Sound travels slower than light.

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).

Name two musical instruments which produce sound by vibrating strings.

Electric current is to be passed from one body to another. For this purpose, the two bodies must be joined by 

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.

If air and cloud were good conductors of electricity, do you think lightning could occur? Explain.

Identify the lightning conductor and the copper plate in the following figure.

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?

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?

Explain how does lightning conductor protects a building from getting struck by lightning.

Explain how lightning takes place.

Explain why it is safer to use a wireless telephone instead of a landline telephone during lightning.

What precautions would you take if lightning occurs while you are outside the house?

What happens to light when it gets dispersed? Give an example.

Burning of wood and coal causes ______ of air.

Fire produced by oil cannot be controlled by ______.

Give reasons.

Water is not used to control fires involving electrical equipment.

Explain how CO₂ is able to control fires.

It is difficult to burn a heap of green leaves but dry leaves catch fire easily. Explain

Which zone of a flame does a goldsmith use for melting gold and silver and why?