PART - A (PHYSICS)
I. Multiple choice questions: 2×1=2
1. The instrument used to measure potential difference and its mode of connection in an electric circuit among the following is
(A) Ammeter, in series connection
(B) Voltmeter, in series connection
(C) Voltmeter, in parallel connection
(D) Ammeter, in parallel connection
Ans: (C) Voltmeter, in parallel connection
2. Observe the following table :
The correct conclusion related to the given lenses is
(A) A ; concave lens and B ; convex lens
(B) A ; convex lens and B ; concave lens
(C) Both are convex lenses
(D) Both are concave lenses
Ans: (B) A ; convex lens and B ; concave lens
II. Answer the following questions :
3. State the right hand thumb rule.
Ans:
Imagine you are holding a current carrying straight conductor in your right hand such that the thumb is pointing towards the direction of current. Then the fingers wrapped around the conductor give the direction of magnetic field.
4. Draw the symbol diagram of ‘Variable resistance (Rheostat)’ used in an electric circuit
Ans:
III. Answer the following questions :
5. List the factors on which the resistance of a conductor depends.
Ans:
★ Length
★ Area of cross section
★ Temperature
★ Nature of materials
6. Define the following :
i) Tyndall effect
ii) Dispersion of light.
Ans:
i) The scattering of a beam of light by colloidal particles.
ii) The splitting of white light into its component colors when passing through a prism.
7. Observe the given schematic diagram. What is the direction of force acting on the electron ? Justify your conclusion.
Ans:
★ Into the paper
★ According to Fleming’s Left-Hand Rule
★ current opposite to electron flow.
IV. Answer the following questions : 3×3=9
8. What is Myopia ? Mention the causes and remedy for this defect.
OR
Stars twinkle but planets do not twinkle. Why ?
Ans:
★Cannot see distant objects clearly.
Causes:
★ Decrease in focal length
★ Elongation of eyeball
Correction:
★ Concave lens
OR
★ Stars are point sources far away.
★ Planets closer to the earth than star.
★ Extended source of light from planets nullify the twinkling Effect.
9. How soft iron rod can be converted into an electromagnet using a solenoid ? How can the magnetic field of this electromagnet be increased ?
OR
Explain an activity for drawing the field lines around a bar magnet using a compass needle.
Ans:
★ Insert soft iron rod inside solenoid and pass current.
Increase strength by:
★ Increasing number of turns
★ Increasing current
OR
★ Take a small compass and a bar magnet. Place a magnet on a sheet of white paper fixed on a drawing board. Mark the boundary of the magnet.
★ Place the compass near the north pole of the magnet mark the position of two ends of the needle.
★ Now move the needle to a new position such that the south pole occupies the position previously occupied by its north pole.
★ In this way proceed step by step till we reach the south pole of the magnet. Join the points marked on the paper by a smooth curve. This represents field line.
★ Repeating above procedure we can draw as many lines as possible.
10. Draw the ray diagram that shows the image formed when an object is kept between 2F1 and F1 of a convex lens. Mention the size and position of the image.
Ans:
Position of the image-beyond 2F2
Size of the image: Enlarged
V. Answer the following questions :2×4=8
11. a) The refractive indices of water and ice respectively are 1·33 and 1·31. In which of these two medium the light travels faster ? Why ?
b) Explain why the emergent ray is parallel to the incident ray when light refracts through a rectangular glass slab.
OR
a) A pencil is partially immersed in water. Then the pencil appears to be bent.
b) Explain this phenomenon. Write any two differences between spherical mirror and spherical lens.
Ans:
a)
★ Light travels faster in ice
★ because lower refractive index
b)
★ because the opposite faces of a rectangular glass slab are parallel,.
★ due to this the refractive index change is equal and opposite at the two parallel air-glass and glass-air interfaces
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