Secondary School (English Medium) (5 to 8) Class 8 - CBSE Question Bank Solutions for Science

What are the three essential requirements to produce fire? How fire extinguisher is useful for controlling the fire?

State whether the following statement is True or False. Correct the false statement.

Deforestation leads to an increase in the water holding capacity of the soil.

Can a forest regenerate naturally in a short period of time?

Is deforestation associated with global warming? Explain.

How does deforestation lead to frequent floods and droughts?

In the following figure, two boys A and B are shown applying force on a block. If the block moves towards the right, which one of the following statements is correct?

Whenever the surfaces in contact tend to move or move with respect to each other, the force of friction comes into play

In the following figure, a boy is shown pushing the box from right to left. The force of friction will act on the box

To sharpen the blade of a knife by rubbing it against a surface, which of the following will be most suitable?

A boy rolls a rubber ball on a wooden surface. The ball travels a short distance before coming to rest. To make the same ball travel longer distance before coming to rest, he may

The handle of a cricket bat or a badminton racquet is usually rough. Explain the reason.

When the cutting edge of a knife is put against a fast rotating stone to sharpen it, sparks are seen to fly. Explain the reason.

We have two identical metal sheets. One of them is rubbed with sand paper and the other with ordinary paper. The one rubbed with sand paper shines more than the other. Give reason.

Suppose a stick is struck against a frying pan in vacuum. Will the frying pan vibrate? Will we be able to hear the sound? Explain.

Which one of the following solutions will not conduct electricity?

Observe the circuit given in the figure.

Boojho set up this circuit for purification of copper. What will be the nature of – (i) plate A (ii) plate B (iii) and the solution.

Explain the process of purification.

Observe the following circuit given in the figure.

Current does not flow in the circuit, if there is a gap between the two wires. Does it indicate that air is a poor conductor of electricity? Does air never conduct electricity? Explain.

Boojho made the circuit as shown in the figure. He wanted to observe what happens when an electric current is passed through water. But he forgot to add a few drops of lemon juice to water. Will it make any difference to his observations? Explain.

Observing that the bulb does not glow in the circuit shown in the following figure A, Boojho changed the circuit as shown in the following figure B. He observed deflection in the magnetic compass.

A	B

1. What does the deflection in magnetic compass indicate?
2. Why did the bulb not glow in the following figure A?
3. What would be the effect of increase in the number of turns in the coil wound around the magnetic compass in the following figure B?
4. What will be observed if the number of cells are increased in the circuit shown in the following figure B?

Part of the eye which controls the light entering is called