DEVI SECONDARY SCHOOL Sub Code: 1011
Class : XI Time : 3 hrs
Subject : Physics FM : 75
[Candidates are required to give their answer in their own words as for as practicable the figure on the right side indicates full marks.]
Choose the best alternative to the following questions. (1×11=11)
1. Which of the following have same dimension?
a. Angular momentum and linear momentum b. Work and power
c. Work and Torque d. Torque and pressure
2. The maximum number of components of a vector that can be splitted are….
a.2 b. 3 c.4 d. infinite
3. A particle moving in a circle with a uniform speed has constant…..
a. Velocity b. acceleration c. Kinetic energy d. displacement
4. The acceleration due to gravity at the equator is g. its value at the pole is…..
a. less than at equator b. greater than g c. less than g d. none of the above
5. The deviation produced by a prism doesn’t depend on…..
a. Angle of prism b. Material of prism c. The angle of incidence d. Size of the prism
6. Which of the following remains constant during refraction?
a. Velocity b. Wavelength c. Amplitude d. Frequency
7. In the formation of a rainbow, the light from the sun on water droplets undergoes which of the following phenomenon phenomena?
a. dispersion only b. only total reflection c. dispersion and total internal reflection d. scattering
8. what is the power of a lens whose focal length is 0.5 m ?
a. 1 D b. 0.5 D c.2 D d. 2.5 D
9. Holes are majority charge carriers in……….
a. N-type semiconductors b. ionic solids c. P-type semiconductors d. metals
10. The capacitance of a parallel plate capacitor increases with…….
a. decrease of its area b. increase of its distance c. increase of its area d. none of above
11. current in a metallic conductor is due to………
a. flow of electrons b. flow of ions c. flow of electrons and ions both d. flow of molecules.
Answer the following questions. (8×5=40)
- a. Find the angle of projection at which the range the horizontal range and maximum height of projectile are equal. 
- An object is dropped from the top the tower of height 156.8 m and the same time another object is thrown vertically upward with the velocity of 78.4ms–1 from the foot of the tower, when and where the two objects meet? 
14. a. Which physical property of molecules of a gas gives a measure of temperature? 
b.A steel wire 8m long and 4 mm in diameter is fixed to two rigid supports. Calculate the increase in tension when the temperature falls by 100C. Given linear expansivity of steel, = 12×10-6/K, Young’s modulus for steel, Y = 2×1011 N/m2. 
c. Define temperature gradient in an object. 
15. a. Why do we prefer white colored clothes in summer and black colored clothes in winter? 
b. A slab of stone of area 0.36m2 and thickness 10cm is exposed on the lower surface to steam at 100C. A block of ice at 00C rests on the upper surface of the slab. In one hour 4.8 kg of ice is melted. Calculate the thermal conductivity of stone.
[Latent heat of fusion ice = 3.36×105J/kg] 
16 a. “A concave mirror is called converging mirror. Why? 
b. State one daily application of convex Mirror. 
c.A ray of light is incident at 60° in air on an air-glass plane surface. Find the angle of refraction in the glass (µ for glass = 15). 
a. Define principal focus. Why is it called so? 
b. i. Define power of lens 
ii. The radii of curvature of double concave lens are 30 cm and 60 cm. The refractive index of its glass is 15 Calculate the focal length of the lens. 
17.a. What is meant by quantization of charge? 
b. Describe the effect of permittivity on force between two charges. 
“Nothing happens to a bird standing on high power line but a man gets fatal shock by touching to it”, why? 
18. a. How will you arrange 3 capacitors each having the capacity of 2F, to get a capacitor of capacity 3F? 
b. Two horizontal parallel plates, each of area 500 cm2 are mounted 2 mm apart in a vacuum. The lower plate is earthed and the upper one is given a positive charge of 0.05 C. Deduce values for
i. the capacitance between the two plates and
ii. electrical energy stored in the system 
19. a. A wire is stretched to double its length. What happens to its resistance and resistivity? 
b. a potential difference of 4.5v is applied between the end of a wire that is 2.5 m long and has radius of 0.654mm. The resulting current through the wire is 17.6A . what is the resistivity of the wire ?
Given long answer in the following questions. [3×8=24]
- a. Why is it easier to hold down a 10 kg body in your hand at your side than to hold it with your arm extended horizontally? 
b. A 550 N physics student stands on a bathroom scale in an elevator. As the elevator starts moving, the scale reads 450N.
i. Find the acceleration of the elevator (magnitude and direction). 
ii. What is the acceleration if the scale reads 670N? 
c. What is the difference between center of gravity and center of mass of a system? 
21. a. Derive an expression for the energy stored in stretched wire. Define the term energy density of a body under strain. 
b. What is the percentage increase in the length of a wire of diameter 2.5 mm stretched by a force of 100 kg? Young’s modulus of elasticity of the wire is 12.5 × 1011 dyne cm–2. 
c. Iron is more elastic than rubber. Why? 
a. Differentiate conservation of kinetic energy and conservation of linear momentum. 
b. Show that the relative velocity of approach before collision is equal to the relative velocity of separation after collision. 
c. Derive an expression for the banking angle. 
22. a. Define atomic mass unit and convert it into MeV. 
b. The energy liberated in the fission of a single atom of uranium – 235 is 3.2 × 10-11 J. Calculate the power production corresponding to the fission of 1gm of uranium per day.
(Assume Avogadro constant = 6.0 × 1023 mole-1). 
c. What is the difference between intrinsic and extrinsic semiconductors? 
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