Class 8 Science Chapter 11 MCQ

When an electric current is passed through a conducting solution, it causes chemical reactions. The resulting effect is called “chemical effect of current”. When an electric current is passed through a bulb, its filament gets heated to a high temperature and bulb starts glowing. The resulting effect is heating effect of current. Whenever an electric current is passed through a circuit, a magnetic effect is produced around it. The resulting effect is magnetic effect of current. Thus, an electric current can produce chemical, heating and magnetic effects.

Here, all the statements are correct. Hence, your answer will be option [D].

Bulb in the set-up A glows more brightly because higher current is flowing through the circuit in set up A, as solution A is better conductor of electricity than that of B.

Here, all the statements are correct. Hence, your answer will be option [D].

Here, all the statements are correct. Hence, your answer will be option [D].

Here, all the statements are correct. Hence, your answer will be option [D].

Water is a chemical compound and hydrogen and oxygen are elements. When electric current is passed through water. A chemical compound “water” has been decomposed into two elements, hydrogen and oxygen, by the action of electric current. So, this reaction is an example of chemical effect of electric current. The breaking up of water into hydrogen and oxygen is actually a “chemical decomposition reaction” caused by passing an electric current through acidified water which is a conducting liquid. 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.

Here, all the statements are correct. Hence, your answer will be option [D].

The passage of an electric current through a conducting solution causes chemical reactions. As a result, change of colour of solution occurs. This indicates the chemical effect of current.

Here, all the statements are correct. Hence, your answer will be option [D].

Here, all the statements are correct. Hence, your answer will be option [D].

Distilled water is a poor conductor or non-conductor of electricity because it does not contain any dissolved salts in it which can provide it ions to conduct electricity. Thus, distilled water is pure water and it does not conduct electricity.

As we know that electrolytes are of two types; strong electrolytes and weak electrolytes. A strong electrolyte is a liquid which conducts electricity very well but a weak electrolyte is a liquid which conducts electricity to a lesser amount because it contains a lesser number of ions. As example of weak electrolytes are; vinegar or acetic acid solution, lemon juice, carbonic acid solution, ammonium chloride solution, rain water, tap water etc.

Here, all the statements are correct. Hence, your answer will be option [D].

Here, all the statements are correct. Hence, your answer will be option [D].

Here, all the statements are correct. Hence, your answer will be option [D].

Here, all the statements are correct. Hence, your answer will be option [D].

Sugar solution in dilute water does not make ions and is a poor conductor of electricity. Therefore, it will not make the current to flow through it and the bulb will not glow.

The decomposition produced by passing current through a conducting liquid is called “Electrolysis”.

We should follow all the three methods, except one which is option [D]. A distilled water salt of the metal to be purified is taken as electrolyte is not required for electrolyte. Hence, your answer should be option [D].

When electric current flows through a conducting solution, it causes a chemical reaction or chemical change. The chemical reaction is brought about by an electric current may produce one or more of the following effects. Such as: i)bubbles of a gas may be formed on the electrodes ii)deposits of metals may form on electrodes iii)change in colour of solution may occur These are some of the chemical effects of the electric current. But formation of a precipitate is not produced by the chemical reactions by an electric current.

The electroplating of chromium on metal object is called chrome. This procedure is used to reduce corrosion and for decorative purpose. Trivalent chromium plating is done on graphite to avoid oxidation reaction taking place in it. Here, chromium chloride or chromium sulphate is used for electroplating. This is majorly used to make the product thicker. Chromium is plated on steel for decorative purpose and make the metal corrosive resistant. It is used in car parts and utensils. Bakelite and teflon both are special type of plastic.

Here, all the statements are correct. Hence, your answer will be option [D].

The device which can be used to detect very small current flowing in an electric circuit is light emitting diode or LED.

The copper acts as cathode (+) and iron acts as anode (-). This setup is used for electroplating. The electrochemical reaction between copper and iron is: Fe (iron) + CuSO₄ (copper sulphate) = FeSO₄ (ferrous sulphate) + Cu (copper) When electricity is passed through electrode then the copper sulphate ionizes to form copper ions and sulphate ions. Copper (positive) ions move towards iron (negative) ions and this forms a layer of copper over iron which is called as electroplating.