answer the all questions please
Answers
19. An armature is a soft iron core on which the coil is wound plus the coils. It helps to enhance the power of the motor.
20. Basic substances like CaCO₃ and MgCO₃ can be added to the soil to neutralize its acidity. This is because plants have a narrow pH range for their healthy growth.
21. Refer to NCERT textbook class 10 Pg 9, Figure 1.6 for the diagram.
22. The black coating over silver coins is AgS.
Ag+H₂S----> AgS + H₂ (This is only one of the many ways in which silver sulphide is formed.
The green coating over copper coins is basic copper carbonate.
Cu+H₂O+O₂+CO₂ -----> Cu(OH)₂ . CuCO₃
23. Herbivores have longer intestines than carnivores because herbivores ingest cellulose which is a complex carbohydrate and is difficult and more time taking for simplification. On the contrary, meat is easier to digest.
OR
It is necessary to separate oxygenated and deoxygenated blood in the body of mammals and birds because they are warm blooded organisms and need to expend energy to constantly maintain their body temperature.
24. → Simply placing a magnet produces a magnetic field around it.
→ A current carrying conductor produces a magnetic field around it.
OR
→ Magnetic lines of forces form closed, continuous loops.
→ Magnetic lines of forces never intersect, because at the point of intersection, the compass needs to show two north directions, which is not possible.
25. Refer to NCERT textbook class 10, Pg 115, Figure 7.1 (a).
26. Exocrine glands : →They are duct glands.
→They secrete the enzymes exactly where they are
needed.
Eg. Liver
Endocrine glands : →They are ductless glands.
→ They secrete hormones into the bloodstream and the place of secretion is far away from the target location.
Eg. Pituitary gland
OR
Involuntary Actions
→ These actions are performed under the control of brain.
→ These are the life processes which are performed for our survival.
Eg. Peristalsis, Respiration
Reflex Actions :
→ These actions are under the control of spinal cord.
→ These actions help to provide a quick response instead of the long thinking process.
Eg. Withdrawal of hand from a flame.
27. Refer to NCERT textbook class 10, Pg 52, Figure 3.12.
28.
Concave mirror:
→ This mirror has the caved-in part as the reflecting surface, whereas the bulging part is silvered.
→ It produces a real and inverted image in all the cases except when the object is placed between P and F.
→ It is used in solar cookers for concentrating the light rays of the sun, in dentist mirrors to see enlarged and virtual, erect image of tooth (object placed between P and F) or in shaving mirrors.
Convex Mirrors:
→ This mirror has the bulged out part as reflecting surface while the caved-in part is silvered.
→ It always produces a diminished, virtual, erect, image.
→ It is used as vigilance mirrors in shops, as rearview mirrors in vehicles (to provide a wider field of view) or in parking lots or sharp turnings in hilly places.
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