NCERT Class VIII Science Solutions: Chapter 14-Chemical Effects of Electric Current Part 3 (For CBSE, ICSE, IAS, NET, NRA 2022)

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Question 12:

Boojho made the circuit given in Fig and observed that the bulb did not glow. On Paheli՚s suggestion he added one more cell in the circuit. The bulb now glows. Explain.

As Showing in Fig is a Electrical Circuit


Addition of another cell increased the current through the bulb sufficiently to make it glow.

Question 13:

Paheli set up an experiment using liquid A in the beaker as shown in Fig. 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.

As Showing in Fig is a LED Bulb is Not Working in Liquid A


The current through liquid B could be weak and therefore unable to make the bulb glow. However, it was strong enough for the LED to glow.

Question 14:

Paheli wants to deposit silver on an iron spoon. She took silver nitrate solution in a beaker and setup 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?


The spoon should be connected to the negative terminal of the battery. The other electrode should be made of silver.

Question 15:

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


Tin is less reactive than iron. Tin coating prevents food from coming in contact with iron and thus prevents it from getting spoiled.