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

An electric current can produce

Boojho and Paheli performed experiments taking similar bulbs and cells but two different solutions A and B as shown in the following figure.

Boojho's Experiment	Paheli's Experiment
(A)	(B)

They found that the bulb in the setup A glows more brightly as compared to that of the setup B. You would conclude that

Boojho’s uncle has set up an electroplating factory near his village. He should dispose off the waste of the factory

When electric current is passed through a conducting solution, there is a change of colour of the solution. This indicates

Which of the following metals is used in electroplating to make objects appear shining?

The object to be electroplated is taken as ______ electrode.

One of the most common applications of chemical effect of electric current is ______.

Electroplating of ______ is done on objects like water taps and cycle bell to give them a shiny appearance.

Paheli set up an experiment using liquid A in the beaker as shown in the following figure. She observed that the bulb glows. Then she replaced the liquid A by another liquid B. This time the bulb did not glow. Boojho suggested replacing the bulb by an LED. They observed that the LED glows. Explain.

Paheli wants to deposit silver on an iron spoon. She took silver nitrate (AgNO₃) solution in a beaker and set up a simple circuit for electroplating. Which terminal of the battery should the spoon be connected to? What material should the other electrode be made of? 

Why is tin electroplated on iron to make cans used for storing food?

Observe the following circuits carefully. In which circuit will the bulb glow? Write Yes or No in the blank space provided along each of the circuit given in the figure.

In the circuit given as figure, Boojho observed that copper is deposited on the electrode connected to the negative terminal of the battery. Paheli tried to repeat the same experiment. But she could find only one copper plate. Therefore, she took a carbon rod as negative electrode. Will copper still be deposited on the carbon rod? Explain your answer.

You are provided with a magnetic compass, an empty matchbox, a battery of two cells and connecting wires. Using these objects, how will you make a tester for testing an electric circuit? Draw the necessary circuit diagram and explain.

Look at the figure. Can the image of the child in it be obtained on a screen?

The change in seasons on the earth occurs because

Do stars emit light only during night?

Paheli and Boojho observe a bright object in the night sky which was not twinkling. Paheli says, it is a star and Boojho says it is a planet. Who is correct?

State whether the following statement is ‘True’ or ‘False’.

The planet nearest to us is Jupiter.

State whether the following statement is ‘True’ or ‘False’.

The planets do not emit light of their own.