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

Suppose your writing desk is tilted a little. A book kept on it starts sliding down. Show the direction of frictional force acting on it.

Explain why sportsmen use shoes with spikes.

Give examples to show that friction is both a friend and a foe.

Iqbal has to push a lighter box and Seema has to push a similar heavier box on the same floor. Who will have to apply a larger force and why?

Most liquids that conduct electricity are solutions of ________, _______ and ________.

When the free ends of a tester are dipped into a solution, the magnetic needle shows deflection. Can you explain the reason?

The bulb does not glow in the setup shown in figure list the possible reasons. Explain your answer.

A tester is used to check the conduction of electricity through two liquids, labelled A and B. It is found that the bulb of the tester glows brightly for liquid A while it glows very dimly for liquid B. You would conclude that ______.

Does pure water conduct electricity? If not, what can we do to make it conducting?

In case of a fire, before the firemen use the water hoses, they shut off the main electrical supply for the area. Explain why they do this.

A child staying in a coastal region tests the drinking water and also the seawater with his tester. He finds that the compass needle deflects more in the case of seawater. Can you explain the reason?

Is it safe for the electrician to carry out electrical repairs outdoors during heavy downpour? Explain.

Paheli had heard that rainwater is as good as distilled water. So, she collected some rain water in a clean glass tumbler and tested it using a tester. To her surprise, she found that the compass needle showed deflection. What could be the reasons?

When a glass rod is rubbed with a piece of silk cloth the rod ______.

A charged glass rod attracts a charged plastic straw.

Sometimes, a crackling sound is heard while taking off a sweater during winters. Explain.

Suppose you are in a dark room. Can you see objects in the room? Can you see objects outside the room? Explain.

Phases of the moon occur because

Which of the following reproduces only inside a host cell?

A disease in human beings caused by virus is ______.