CHEMICAL EFFECTS OF ELECTRIC CURRENT

Yor are provided with a magnetic compass, an empty match box,
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.

An electric current is passed through a conducting solution. List
any three possible observations.

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

Paheli wants to deposit silver on an iron spoon. She took silver
nitrate (AgNO3) 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?

Name the effect of current responsible for the glow of the bulb in
an electric circuit.

Will the solution of sugar in distilled water conduct electricity?

Why is a layer of zinc coated over iron?

Fill in the blanks
(a) The object to be electroplated is taken as ____________
electrode.
(b) One of the most common applications of chemical effect of
electric current is ______________.
(c) Small amount of a mineral salt present naturally in water
makes it a______________ of electricity.
(d) Electroplating of ______________ is done on objects like water
taps and cycle bell to give them a shiny appearance.

The process that you saw in Activity 14.7 is used for purification of copper. A thin plate of pure copper and a thick rod of impure copper are used as electrodes. Copper from impure rod is sought to be transferred to the thin copper plate. Which electrode should be attached to the positive terminal of the battery and why?

Prepare a list of objects around you that are electroplated.

Paheli had heard that rain water 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?

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

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?

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.

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.

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

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

(i) liquid A is a better conductor than liquid B.

(ii) liquid B is a better conductor than liquid A.

(iii) both liquids are equally conducting.

(iv) conducting properties of liquid cannot be compared in this manner.

The bulb does not glow in the setup shown in Fig. 14.10. List the possible reasons. Explain your answer.

Name three liquids, which when tested in the manner shown in Fig. 14.9, may cause the magnetic needle to deflect.

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

Fill in the blanks.

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

(b) The passage of an electric current through a solution causes _________ effects.

(c) If you pass current through copper sulphate solution, copper gets deposited on the plate connected to the__________ terminal of the battery.

(d) The process of depositing a layer of any desired metal on another material by means of electricity is called_________.