Time-2 hrs M.M.-70
1. Answer the following: (6)
a) What is the magnification of the image formed by plane mirror?
b) The value of m for the image formed by a convex lens is greater than +1. What is the possible position of the object.
c) How many electrons pass through a lamp in one minute if the current is 300 mA.
d) Two lenses of power +5.0D and-2.5D are placed in contact, find the focal length and the power of combination.
e) Write two characteristics of fuse wire.
f) Complete the given ray diagram (ask for diagram)
2. A wire of resistance 20 Omega is drawn out so that its length is increased to twice its original length. Determine the new resistance. (3)
3. A torch bulb is rated 2.5V and 750mA. Calculate its resistance, power and energy consumed by it in four hours. (3)
4. Calculate the net resistance and the current flowing through each resistance in the given circuit. (ask for circuit diagram) (3)
5. Why the sky appears red at the time of sunrise and sun set? (3)
6. Define the following: (i) resistivity (ii)one ohm resistance. (iii) one KWH (iv) refractive index (v) principal focus of a concave lens. (5)
7. If an image of a candle flame, magnified six times, is to be thrown on a wall by a convex lens of focal length 18cm,at what distance must the candle flame be placed from the lens.
8. A concave mirror produces a magnification of ½ when an object is placed at 60cm from it. Where should the object be placed so that a virtual image of double of the size is formed. (3)
9. What is the cause of myopia? Show with diagram also, How is it corrected? (3)
10. A 25W and 100W bulbs are joined in series and connected to the mains. Which bulb will glow brighter and why?
11. Answer the following: (6)
a)Name one strategic metal.
b)Name one amphoteric oxide?
c)What is the formula of P.O.P
d)Name two metals which do not react with oxygen
e)Name the calcium comound used to disinfect water.
f)Complete the reaction Mg + HNO3(very dil)
12. Between copper and sodium which metal is more reactive , Explain with two reasons.
13. What type of reaction takes place in the following: (4)
a)Zinc strip is dipped in copper sulphate solution
b)Lime stone is heated
c)Electricity is passed through water
e)Silver bromide is exposed to sunlight
14. How copper is refined by electrolytic refining? (3)
15. Why does a milkman adds a very small amount of baking soda to fresh milk? Why does this milk takes longer time to set as curd? (2)
16. Why metals displace hydrogen from water while non-metals do not? Explain your answer. (3)
17. What happens when (3)
a) Iron oxide and Aluminium powder is heated by burning magnesium ribbon
b) Strip of copper is kept immersed in silver nitrate solution
c) Dry HCL gas comes in contact of litmus paper.
18. What do mean by corrosion of metals. What are the different methods of preventing it? (4)
19. A certan metal X lies between potassium and Magnesium in the reactivity series.Answer the following: (3)
a)What will happen when the metal is added to cold water
b)What reaction takes place between metal and dil HCL
20. Draw the electronic dot structure of the following: (4)
(a) Magnesium oxide (b)C2H6 (c)Water (d) Calcium chloride
Also tell the nature of compound
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