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.
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.
Ans. When an electric current flows through a conducting solution, it causes following chemical change:
i. Bubbles of gas or gases may be formed on the electrodes.
ii. Deposits of metals may form on electrodes.
iii. Changes in colour of solutions may occur.
Ans. (i) liquid A is a better conductor than liquid B.
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.
Ans. 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.
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.
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.
Ans. Examples of electroplating
i. Chromium plating is done on many objects such as car parts, bath taps, kitchen gas burners, bicycle handlebars, wheel rims and many others.
ii. Jewellery makers electroplate silver and gold on less expensive metals.
iii. Tin cans, used for storing food, are made by electroplating tin onto iron.
iv. A coating of zinc is deposited on iron to protect it from corrosion and formation of rust.
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