30. An electric heater of resistance 8 2 draws a 15 A from the service mains 2 hours. Calculate ti
rate at which heat is developed in the heater.
31. Why is tungsten used almost exclusively for filament of electric lamps?
32. Draw a schematie diagram of a circuit consisting of a battery of three cells of 2v each, a 5 92
resistor, And 8 22 resister, and a 12 Q resistor and a plug key, connected all in series.
33. Draw a magnetic field lines around a bar magnet
34. Name some devices in which electric motors are used.
35. Write events occurs during photosynthesis.
36. What is hydrotropism? Give an example.
3X5=15
37. What are the functions of digestive enzymes?
38. Five solutions A, B, C, D, and E when tested with universal indicator showed pH as 4,1,
respectively. Which solution is
[a]
neutral ?
[b]
Strongly alkaline ?
Answers
Ans 30 . The rate at which work is done by a source of emf in maintaining an electric current through a circuit is called the electric power of the circuit. = 1800 Watt. Thus the rate at which heat is developed in heater is 1800 Watt.
Ans 31.The melting point and of Tungsten is an alloy which has very high melting point and very high resistivity so does not burn easily at a high temperature.
Ans 32.this answer is to be drawn so i have put the picture up.
Ans 33.this answer is also to be drawn so i have put the picture up.
Ans 34.Electric motors are used in electric fans, mixers, water pumps, washing machines, etc.
Ans 35.The three events that occur during the process of photosynthesis are: (i) Absorption of light energy by chlorophyll. (ii) Conversion of light energy to chemical energy and splitting of water molecules into hydrogen and oxygen. (iii) Reduction of carbon dioxide to carbohydrates.
Ans 36.An example of hydrotropism is the movement of plant roots towards water. It is a positive hydrotropism because the roots move towards the stimulus
Ans 37.Digestive enzymes play a key role in breaking down the food you eat. These proteins speed up chemical reactions that turn nutrients into substances that your digestive tract can absorb. Your saliva has digestive enzymes in it. Some of your organs, including your pancreas, gallbladder, and liver, also release them.
Ans 38.Five solutions A, B, C, D, and E, when tested with a universal indicator, showed pH as 4, 1, 11, 7 and 9, respectively, which solution is
(a) neutral (b) strongly alkaline (c) strongly acidic
(d) weakly acidic (e) weakly alkaline
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