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

3

(a)

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.

3

(a)

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

3

(a)

Explain in brief the procedure of glowing of bulb in a liquid

3

(a)

Explain, how can we purify the impure metals

3

(a)

Observe the following circuit given in 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.

3

(a)

We should throw conducting materials used in electroplating far away from residential area. Explain why.

3

(a)

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?

3

(a)

Observe figure

Which of these two circuits A or B shows the correct observation?

3

(a)

Experimentally prove that the solutions of acids, bases and salts conduct electricity.

3

(a)

What are the chemical effects of electric current? Explain with an example

3

(a)

Discuss two methods of testing a conductor or an insulator

3

(a)

Why should we not experiment with the electric supply from mains?

3

(a)

One day Rohan went to his friend's house. He was surprised to see that most of the electrical appliances at his house were functional. For example, tubelights and fans in all rooms, two TV's, computer, light of toilet and kitchen all were switched on. Rohan told his friend that this is not the way to use electricity. Now the question arises whether this habit of consuming electrical energy is acceptable or not. Will it not affect the economical condition of family as well as the Nation? How?

3

(a)

Last Wednesday, Suhail woke up late in the morning. So, he saw the time and suddenly realised that he got late for an interview, which he was supposed to give after reaching the venue by the right time. Immediately, he turned on the geyser but it did not work. He got more tensed, then he used an electric iron rod through which he got some boiled water for his bath. Actually, there was an earthing problem in the switch board about which he was unaware. He was barefooted and was just about to switch on the electric iron rod but was restricted to do so by his room partner living with him. It could be dangerous for Suhail.
(i) Explain in brief what could have happened with Suhail if he had switched on the electric iron rod barefooted.
(ii) Mention the values showed by Suhails room partner.

3

(a)