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DAV School Question Papers Class-VIII Summative Assessment I (Year 2012-13)   Question Papers Class-VIII Summative Assessment I (Year 2012-13) English Course A English Course B Mathematics Social Studies ( English) Social Studies ( Hindi) Science and Technology Hindi Sanskrit Punjabi Dharam Shiksha Moral Education Hindi Lower Question Papers of Class-VIII Summative Assessment II (Year 2012-13) English Course A English Course B Mathematics Social Studies ( English) Social Studies ( Hindi) Science and Technology Hindi Sanskrit Punjabi Dharam Shiksha Moral Education Hindi Lower Thanks to : http://daveduboard.org/

Central Public School,Samastipur and Sadhana Devi Vidyapith Assignment SA-1 Chapter: Magnetic Effects of Electric Current Section-A [1marks] 1. What does the direction of thumb indicate in the right-hand thumb rule? 2. What is the frequency of alternating current in India? 3. How will you use a solenoid to magnetize a steel bar? 4. An alternating electric current has a frequency of 50 Hz. How many times does it change its direction in one second? 5. Name devices which produce: (i) alternating current, (ii) direct current. 6. Name the physicist who discovered the magnetic effect of the electric current. 7. A straight copper conductor is held parallel to the axis of a freely suspended magnetic needle such that the conductor is under the needle and the current is flowing from south to north. In which direction the north of magnetic needle will move? 8. If a copper conductor carrying a current is held in north-south direction, in which direction will its magnetic fiel

Q. How is NH4OH used as a laboratory reagent? Answer:  NH4OH is used to detect cations in their salt solutions by precipitating their hydroxides whose colour and solubility in excess NH4OH, identifies them. Q. Though NaHSO 4  solution releases H +  ions, why is it not called an acid? Answer:  NaHSO 4  solution is not called an acid because an acid should release only H +  ions as positive ions and not any other positive ions. But NaHSO 4  is solution releases H +  ions as well as Na +  ions also as positive ion. Q. How would you distinguish between baking powder and washing soda by heating? Answer: Sodium hydrogencarbonate on heating gives CO2 gas which will turn lime water milky whereas no such gas is obtained from sodium carbonate. 2NaHCO3 ---Heat → Na2CO3 + H2O + CO2      Na2CO3.10H2O -Heat → Na2CO3 + 10H2O Q. Why aqueous solution of sodium carbonate is basic in nature? Answer: Sodium bicarbonate is an amphoteric compound. Aqueous solutions are mildly alkaline due