Chemical Effects of Electric Current

Q19. When the free ends of a tester are dipped into a solution, the magnetic needle shows deflection. Can you explain the reason?

Ans. The deflection in magnetic needle shows that the circuit is complete and the solution conducts electricity.

Q20. Which metal is usually electroplated on car parts such as bumpers and bicycle handlebars made of steel?

Ans. Chromium is usually electroplated on car parts such as bumpers and bicycle handlebars made of steel.

Q21. Which metal is electroplated on iron for making cans and why?

Ans. Tin is electroplated on iron for making cans because tin is less reactive than iron. Thus, food does not come into contact with iron and is protected from getting spoilt.

Q22. Why is the current in the circuit weak?

Ans. Though a material may conduct electricity, it may not conduct it as easily as a metal. As a result, the circuit of the tester may be complete and yet the current through it may be too weak to make the bulb glow.

Q23. Why do brand new cycles have shiny handlebars and wheel rims what will happen if these are scratched?

Ans. A brand new bicycle has shiny handlebar and wheel rims. However, if these are accidentally scratched, the shiny coating comes off revealing a not so shiny surface beneath.

Q24. Why is it dangerous to touch a working electrical appliance with wet hands?

Ans. It is dangerous to touch a working electrical appliance with wet hands because the tap water is a good conductor of electricity due to which it may conduct electric current and gives us an electric shock.

Q25. Write two common application of the chemical effect of electric current.

Ans. Two common application of the chemical effect of electric current are:

                         i.        Electroplating of metals

                        ii.        Purification of metals

Q26. For electroplating copper on an iron object, which terminal of the battery (positive or negative) is connected to the iron object?

Ans. In the process of electroplating, the metal to be electroplated is taken as cathode (negative) and the one used for coating is chosen as the anode (positive). Thus, negative terminal will be connected to the iron object.

Q27. 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.

Ans. Water is a conductor of electricity, so if the electricity supply is not cut off and firemen come in contact with wet electric switches, electric wires and other electrical appliances, they may get electrocuted.

Q28. Why the bulb glows when the electric current passes through it?

Ans. Due to the heating effect of current, the filament of the bulb gets heated to a high temperature and it starts glowing. However, if the current through a circuit is too weak, the filament does not get heated sufficiently and it does not glow.

Q29. What is meant by the chemical effect of electric current? Give an example.

Ans. The passage of an electric current through a conducting liquid causes chemical reactions. The resulting effects are called chemical effects of currents. Example – Deposit of metal formed when electric current is passed through copper sulphate solution (during electroplating).

Q30. Which properties of chromium metal make it suitable for electroplating?

Ans. The properties of chromium metal that make it suitable for electroplating are:

                         i.        It has a shiny appearance.

                        ii.        It does not corrode.

                       iii.        It resists scratches.

Q31. Name three liquids, which when tested in the manner shown in Figure, may cause the magnetic needle to deflect.

Image from NCERT

Ans. Tap water, vinegar and lemon juice are conductors of electricity. Most liquids that conduct electricity are solutions of acids, bases and salts.