26 November 2011

8th physics Chemical effects of electric current Assignments

Q1. Do liquids also conduct electricity? Name two liquids which conduct electricity & two liquids which do not conduct electricity.
Q2. Name a device which glows even when a weak electric current passes through it.
Q3. Write full form of LED.
Q4. 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 compass is used?
Q5. Is it safe for the electrician to carry out electrical repairs outdoors during heavy downpour? Explain.
Q6. When electric current is passed through acidified water, then hydrogen & oxygen are formed. What type of effect of current is illustrated by this statement?
Q7. State some of the characteristics of chemical changes brought about by the chemical effect of electric current.
Q8. Name the metal which is usually electroplated on car parts such as bumpers & bicycle handlebars made of steel.
Q9. An iron key is to be electroplated with copper. Draw a labeled sketch of the experimental set up used for this purpose.
Q10. Name two metals which are usually electroplated on cheaper metals for making jewellery (or ornaments).
Q11. You are required to do electroplating of copper on an iron object. Name the positive electrode (anode) & the electrolyte you will use for this purpose.
Q12. Write a short note on electroplating.
Q13. Why does compass needle show more deflection when you test sea water, compared to ordinary water?
Q15. Name a liquid which when poured in the beaker may cause magnetic needle to deflect. Name the possibilities if a bulb in tester does not glow (it is for sure that liquid is conducting).

Q16. What happens to the needle of a magnetic compass kept nearby when electric current is switched on in a wire? Why does this happen?
Q17 Iron is used in bridges & automobile to provide strength. Which metal is electroplated on iron to protect it from corrosion?
Q18. We should never handle electrical appliances with wet hands or while standing on a wet floor. Why?
Q19. When the free ends of a conductivity tester (made by using a battery connected to a wire wound around a compass) are dipped into the following solution, then in which  solution or solutions the compass needle shows deflection. Solutions are: Lemon juice, Vinegar, Tap water, Vegetable oil, milk, Honey.
Q20. Why does an electric bulb glow when a current passes through it?
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