Effects of Electric Current
Q32. Is it safe for the electrician to carry out electrical
repairs outdoors during heavy downpour? Explain.
Ans. It is not safe for the electrician to carry out
electrical repairs outdoors during heavy downpour because rainwater being a
conductor of electricity may cause electrocution of the electrician.
Q33. 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?
Ans. The compass needle deflects more in the case of
seawater because due to the presence of a large amount of dissolved salts in
it, sea water is a much better conductor of electricity than drinking water.
Q34. What are the chemical effects of electric current?
Ans. When an electric current flows through a
conducting solution, it causes following chemical change:
Bubbles of gas or gases may be formed on
Deposits of metals may form on electrodes.
Changes in colour of solutions may occur.
Q35. A tester is used to check the conduction of electricity
through two liquids, labeled 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
(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
Ans. (i) liquid A is a better conductor than liquid B.
Q36. What happens when electric current is passed through
Ans. When electrodes
are immersed in water, and a current is passed through acidified water, then
oxygen gas is formed at the positive electrode which is connected to the
positive terminal of the battery and hydrogen gas is formed at the negative
electrode which is connected to the negative terminal of the battery.
Q37. Tap water conducts electricity whereas distilled water does
not. Give reason.
Distilled water is a poor conductor of electricity because it does not contain
any dissolved salts in it which can provide it ions to conduct electricity. The
distilled water becomes a good conductor of electricity on dissolving a little
salt in it. The water that we get from taps is not pure. It may contain several
salts dissolved in it. This water is thus a good conductor of electricity.
Q38. Why is electroplating useful?
Ans. Electroplating is a very useful process. It is
widely used in industry for coating metal objects with a thin layer of a
different metal. The layer of metal deposited has some desired property, which
the metal of the object lacks. For example, chromium plating is done on many
objects such as car parts, bath taps, kitchen gas burners, bicycle handlebars,
wheel rims and many others.
Q39. Paheli had heard that rainwater is as good as distilled
water. So she collected some rainwater 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?
Ans. Rainwater is said to be pure water. But when
rainwater falls to the earth through the atmosphere, it dissolves acidic gases
such as carbon dioxide, sulphur dioxide and nitrogen oxides to form acids such
as carbonic acid, sulphuric acid and nitric acid. Due to presence of acids in
it, rainwater becomes a conductor of electricity.
Q40. Prepare a list of objects around you that are
Ans. Examples of electroplating
Chromium plating is done on many objects
such as car parts, bath taps, kitchen gas burners, bicycle handlebars, wheel
rims and many others.
Jewellery makers electroplate silver
and gold on less expensive metals.
Tin cans, used for storing food, are made by
electroplating tin onto iron.
A coating of zinc is deposited on iron to
protect it from corrosion and formation of rust.