Q.1. Which of the following liquids conduct electricity and which do not conduct electricity?
Lemon juice, Milk, Vinegar, Salt solution, Distilled water, Honey, Seawater, Rainwater.
Q.2. What is the advantage of using LED over bulb in testing the electrical conductivity of liquids?
Q.3. Which effect of electric current is utilized for detecting the flow of current through a solution
(a) When a torch bulb is used?
(b) When a magnetic compass is used?
(a) Heating effect
(b) Magnetic effect.
Q.4. Distilled water does not conduct electricity. What substances can be added to distilled water in small amounts to make it a good conductor of electricity?
Ans. Salt, acid & base.
Q.5. In case of a fire, before the fireman uses the water hoses to throw water to douse the fire, they shut off the electricity supply for the area. Explain why this is done?
Q.6. When the free ends of a conductivity tester (made by using a battery connected to a wire wound around a compass) are dipped into a solution, the magnetic needle shows deflection. Can you give the reason of this deflection?
Q.7. What effects does electric current produce when flowing through a conducting solution?
Ans. When an electric current flows through the conducting solution, it causes a chemical reaction (or chemical change).
These chemical reactions may produce the following effects:
Q.8. When electric current is passed through acidified water then what is produced at
(a) Positive carbon electrode (anode)?
(b) Negative carbon electrode (cathode)?
(a) Oxygen gas
(b) Hydrogen gas.
Q.9. Which effect of electric current is utilized when a thin layer of chromium metal is deposited on an iron tap? What is this process known as?
Ans. Chemical effect of current is utilized. The process is known as electroplating.
Q.10. What is meant by electroplating? What is the purpose of electroplating?
Ans. The process of depositing a layer of any desired metal on another material, by means of electricity, is called electroplating.
Electroplating is done:
Q.11. Which properties of chromium metal make it suitable for electroplating it on car bumpers, bath taps & bicycle handle, etc., made of iron?
Ans. It has shiny appearance. It does not corrode easily. It resists scratches.
Q.12. Which metal is electroplated on iron for making ‘cans’ used for storing food & Why?
Q.13. On what factors the chemical effect produced by an electric current depends?
Ans. The chemical effect produced by an electric current depends on the nature of conducting solution (through which it is passed) and on the nature of electrodes used for passing the electric current.
Q.14. In the process of purification of copper metal, a thin plate of pure copper and a thick rod of impure copper are used as electrodes & a metal salt solution is used as an electrolyte
(a) Which electrode is connected to the positive terminal of the battery?
(b) Which electrode is connected to the negative terminal of the battery?
(c) Which metal salt solution is taken as electrolyte?
(a) Thick rod of impure copper.
(b) Thin rod of pure copper.
(c) Copper sulphate solution.
Q15. Write down the important points which should be remembered while electroplating?