Question: What is advantage of using LED over bulb in testing the electrical conductivity of liquids?
Ans: LED is used in place of bulb because LED glows even when weak electric current flows in the circuit
Question: 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?
Ans: a) Heating effect b) Magnetic effect.
Question: 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?
Ans: Electric current flowing through the wire produces a magnetic field around it. And this magnetic field of electric current acts on the magnetic needle of compass; deflects it.
Question: What effects does an 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 following effects:
i) Bubbles of gas/es may be formed on the electrodes. ii) Deposits of metals may form on electrodes.
iii) Change in colour of solution may occur.
Question: 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
(i) For protection against corrosion (or rusting). (ii) For decorative purposes.
Question: 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.
Question: Which metal is electroplated on iron for making ‘cans’ used for storing food & Why?
Ans: Tin. Tin metal has shiny appearance, it does not corrode & it is non poisonous. Tin is less reactive than iron. Due to tin plating over the surface of iron, the food does not come in contact with iron and is protected from getting spoilt.
Question: 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), & on the nature of electrodes used for passing the electric current.
Question: 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?
Ans: a) Thick rod of impure copper. b) Thin rod of pure copper. c) Copper sulphate solution.