2010 physics paper solution
 

[CENTER][SIZE="7"]paper 1[/SIZE][/CENTER]

[B]Q.1. Select the best option/answer and fill in the appropriate box on the Answer Sheet.[/B]

[COLOR="Blue"][B](i) If A= 6i-8j, then 4A has the magnitude:[/B][/COLOR]

[B](a) 40[/B]
(b) 10
(c) 20
(d) None of these

[COLOR="Blue"][B](ii) Let A= 2i+6j-3k and B= 4i+2j+k then A.B equals:[/B][/COLOR]
(a) 8i+12j-3k
[B](b) 17 [/B]
(c) 23
(d) None of these

[COLOR="Blue"][B](iii) If V is an operator, then V.V means:[/B][/COLOR]
(a) Gradient of a Scalar field
(b) Curl of a vector field
(c) Divergence of a Vector field [B]
[B](d) None of these[/B] [I](its Laplacian)[/I]
[B]
[COLOR="Blue"](iv) The volume of a parallelepiped bounded by Vectors A,B and C can be obtained from the expression:[/B][/COLOR]
[B](a) ( A x B ).C[/B]
(b) (A.B)x C
(c) ( A x B ) x C
(d) None of these

[COLOR="Blue"][B](v) A force acting on a particle is conservative if:[/B][/COLOR]
(a) It obeys Newton's third law
(b) It obeys Newton's second law
(c) It works equals the change in Kinetic energy
[B](d) None of these[/B] [I](work done in a closed loop = 0 ie. independant of the path)
[/I]

[COLOR="Blue"][B](vi) A torque applied to a rigid object always tends to produce:[/B][/COLOR]
[B](a) A rotational acceleration [/B]
(b) A linear acceleration
(c) Precision
(d) None of these

[COLOR="Blue"][B](vii) When the velocity of a body is constant, its acceleration is:[/B][/COLOR]
(a) Maximum
[B](b) Zero [/B]
(c) Infinity
(d) None of these

[COLOR="Blue"][B](viii) In the absence of external torque the total angular momentum is:[/B][/COLOR]
[B](a) Constant [/B]
(b) Zero
(c) infinity
(d) None of these

[COLOR="Blue"][B](ix) The rate of change of Momentum of the particle is:[/B][/COLOR]
(a) Energy
[B](b) Force[/B]
(c) Impulse
(d) None of these
[B]
[COLOR="Blue"](x) Constructive and destructive superposition of waves is observed in:[/B][/COLOR]
(a) Polarisation
[B](b) Interference [/B]
(c) Diffraction
(d) None of these

[COLOR="Blue"][B](xi) The intensity of a wave is proportional to the square of:[/B][/COLOR]
[B](a) Amplitude [/B]
(b) Time
(c) Intensity
(d) None of these

[COLOR="Blue"][B](xii) The colours in soap bubbles, oil slick etc. in a thin film is due to:[/B][/COLOR]
(a) Diffraction
(b) Polaristaion
[B](c) Interference [/B]
(d) None of these

[COLOR="Blue"][B](xiii) For higher resolution, in a diffraction grating, one needs to have:[/B][/COLOR]
[B](a) Large number of ruling [/B]
(b) Small number of ruling
(c) No rulings at all
(d) None of these
[COLOR="Blue"]
[B](xiv) To produce interference, the sources must be:[/B][/COLOR]
(a) Intense
(b) Incoherent
[B](c) Coherent[/B]
(d) None of these

[COLOR="Blue"]
[B](xv) Interference fringes are of:[/B][/COLOR]
(a) Unequal width
[B](b) Equal width [/B]
(c) Variable width
(d) None of these

[COLOR="Blue"][B](xvi) A Carnot Cycle is:[/B][/COLOR]
(a) a rectangle on a P-V graph
[B](b) bounded by two isotherms and two adiabatics[/B]
(c) any four sided process on a P-V graph
(d) None of these


[COLOR="Blue"][B](xvii) In an Adiabatic process:[/B][/COLOR]
(a) The temperature of the system remains constant
[B](b) The temperature of the system must change[/B] [COLOR="Green"]( doubt)[/COLOR]
(c) The internal energy of the system remains constant
(d) None of these

[COLOR="Blue"][B](xviii) A Carnot Cycle heat engine operates between 227°C and 127° C. Its efficiency is:[/B][/COLOR]
(a) 44%
[B](b) 20% [/B]
(c) 79%
(d) None of these

[COLOR="Blue"][B](xix) Metals pipe carrying water some times bursts in winter because:[/B][/COLOR]
[B](a) Water expands [/B] [B](when it cools on becoming ice )[/B] [COLOR="Green"]( doubt)[/COLOR]
(b) Ice expands when melts
(c) Metal contracts more than water
(d) None of these

[COLOR="Blue"][B](xx) A Fahrenheit thermometer and Celsius thermometer shows the same reading at:[/B][/COLOR]
(a) 200°
[B](b) -40°[/B]
(c) 100°
(d) None of these

[CENTER][SIZE="7"]paper 2[/SIZE][/CENTER]
[B]Q.1. Select the best option/answer and fill in the appropriate box on the Answer Sheet. (20)[/B]

[B](i) A Watt – sec is a unit of:[/B]
(a) Force
[COLOR="Blue"](b) Energy[/COLOR]
(c) Power
(d) None of these

[B](ii) The direction of any magnetic induction effect is such as to oppose the cause of the effect. This is:[/B]
(a) Coulumb's Law
(b) Ampere's Law
[COLOR="Blue"](c) Lenz's Law [/COLOR]
(d) None of these

[B](iii) A magnetic field cannot:[/B]
(a) accelerate a charge
(b) Exert a force on a charge
(c) change the kinetic energy of a charge
[COLOR="Blue"](d) None of these[/COLOR] [I]( F=q v x b )[/I]

[B](iv) The inverse of resistivity is called Conductivity. Its unit is:[/B]
(a) Ohm[SIZE="1"]-1[/SIZE]
(b) ohm-metre
[COLOR="Blue"](c) (ohm-meter)[SIZE="1"]-1[/SIZE] [/COLOR]
(d) None of these

[B](v) An LRC Circuit has R= 4Ω, Xc = 3 and XL=6, the impedence of the circuit is:[/B]
[COLOR="Blue"](a) 5 Ω [/COLOR]
(b) 7 Ω
(c) 13 Ω
(d) None of these

[B](vi) A "step-down" transformer is used to:[/B]
(a) increase the power
[COLOR="Blue"](b) decrease the voltage [/COLOR]
(c) Increase the voltage
(d) None of these

[B](vii) Electrical potential is the potential energy per unit:[/B]
[COLOR="Blue"](a) Charge [/COLOR]
(b) Voltage
(c) Force
(d) None of these

[B](viii) The force on a charge moving with the velocity in a magnetic field B is given by:[/B]
(a) F = (q/v x B)
[COLOR="Blue"](b) F = ( qv x B ) [/COLOR]
(c) F = (qv + B)
(d) None of these

[B](ix) A changing current "i" in any circuit induces an emf "e" in that circuit, which is equal to:[/B]
(a) e = di/dt
(b) E = i dΦ/dt
[COLOR="Blue"](c) e = - L di/dt[/COLOR]
(d) None of these

[B](x) Inductive reactance of an inductor is:[/B]
(a) XL= ω2L
(b) XL = ω/L
(c) e = -L di/dt
[COLOR="Blue"](d) None of these[/COLOR] [I](XL = ω.L )[/I]

[B](xi) The resonant frequency of an LC-Circuit is:[/B]
(a) f = 2Π LC
[COLOR="Blue"](b) f = 1 / 2Π√ LC [/COLOR]
(c) f = 1/ 2LC
(d) None of these

[B](xii) The deliberate addition of an impurity element in a semi-conductor is called:[/B]
[COLOR="Blue"](a) doping [/COLOR]
(b) annealing
(c) mixing
(d) None of these

[B](xiii) The conversion of AC into DC is called:[/B]
(a) amplification
[COLOR="Blue"](b) rectification [/COLOR]
(c) modulation
(d) None of these

[B](xiv) The Laser light is:[/B]
[COLOR="Blue"](a) monochromatic [/COLOR]
(b) coloured
(c) chromatic
(d) None of these

[B](xv) The Laser light may be obtained from:[/B]
(a) quartz crystal
(b) NaCl crystal
[COLOR="Blue"](c) ruby crystal [/COLOR]
(d) None of these

[B](xvi) The emission of photoelectrons in photoelectric effect is dependent on:[/B]
[COLOR="Blue"](a) threshold frequency [/COLOR]
(b) intensity of light
(c) Nature of metal
(d) None of these

[B](xvii) Which one of the following is NOT needed in Nuclear Fission reactor:[/B]
(a) fuel
[COLOR="Blue"](b) accelerator [/COLOR]
(c) moderator
(d) None of these
[B]
(xviii) The half life of a radioactive isotope is 140 days. How many days would it take to loose 3/4 of its initial activities:[/B]
(a) 105 days
[COLOR="Blue"](b) 280 days [/COLOR]
(c) 35 days
(d) None of these

[B](xix) Most of the energy produced in Sun is due to:[/B]
[COLOR="Blue"](a) Nuclear fusion [/COLOR]
(b) Chemical reaction
(c) Nuclear Fission
(d) None of these
[B]
(xx) A U-235 nucleus will split when it captures:[/B]
(a) an α-particle
(b) e.m. radiation
[COLOR="Blue"](c) neutron [/COLOR]
(d) None of these