Guess Paper – 2009
Class – XII
Time allowed: 3 hours Maximum Marks : 70
(i) All questions are compulsory.
(ii) Question numbers 1 to 8 are very short answer type questions, carrying one mark each.
(iii) Question numbers 9 to 18 are short answer type questions , carrying two marks each.
(iv) Question numbers 19 to 27 are also short answer type questions, carrying three marks each.
(v) Question numbers 28 to 30 are long answer type questions, carrying five marks each.
(vi) Use of calculators is not permitted. However, you may use log tables, if necessary.
Q.1 Define the term electric flux. Write its SI unit ?
Q.2What is the work done in moving a charge of 12 nc . b\t two points on an equipotential surface ?
Q.3 What is the order of voltages that can be built up using a Van De Graff generator?
Q.4 What is the angle b/w Electric field and Dipole moment at an axial point?
Q.5 state lenz law. On which law of conservation is it based ?
Q.6 The sequence of bands marked on a carbon resistor is yellow , violet , silver and Gold .W HAT is the value of the resistance ?also give the tolerance.
Q.7 What is the significance of ‘Q’ factor in a series LCR resonant circuit?
Q.8 Name the part of electromagnetic spectrum to which these radiations belong.
Ultraviolet Rays Microwaves ?
Q.9 On the same graph plot the variation of E versus R and V versus R for a point charge.?
Q.10 What does the term LOS communication mean?
Q11 A double convex lens, made from a material of refractive index µ , is immersed in a liquid of refractive index µ2 Where µ2 >µ1 W hat change , if any, would occur in the nature of the lens?
Q.12 Using a suitable graph, explain why nichrome is used in standard resistance coils.
Q.13 state the reason why ground waves can not be transmitted above the frequency range of 1500Khz.
Q.14 Explain why a potentiometer is preferred over a voltmeter for measuring potential differences.
Q.15 Prove that two parallel conductor carrying current in the opposite direction repel each other.Hence deduce an expression for the force per unit length experienced by each conductor?
Q.16 STATE and DEFINE K.V.L. and K.C.L LAW ?
Q.17 The resistivity of a metal X is 3.2 x 10-8 while the free
electron density is 5 x 1028 m-3. Find the drift velocity of
Electrons if a potential gradient of 1 Vm-1 is applied across X.
Q.18 What type of materials are used for making
(a) Permanent magnets
(b) Transformer cores.
Give two line reasons for each
Q.19 IWhy is the ammeter connected in series and voltmeter in parallel in the circuit ?
Q.20 Show that the far field of a solenoid resembles that of a bar magnet. Hence define the magnetic moment of a solenoid.
Q.21 A long cylinder of radius Ro is carrying a current Io ,which is uniformly distributed over its cross section. Derive an expression for the magnitude of magnetic field inside as well as outside the wire. Plot a curve to show the variation of magnetic field with radial distance.
Q.22 Deduce snell’s law of refrective using Huygen’s wave theory?
Q.23 IN INDIA ,domestic power supply is at 220 volt, 50 Hz , while in U.S.A. it is 110 volt , 50 Hz , Give one advantage and Disadvantage of 220 volt supply over 110 V supply ?
Q.24 Use kickoff’s laws to deduce the condition of a balanced wheatstone bridge.
Q.25 Explain mathematically, why the resistance of metals increases while that of semiconductor decreases with the rise in temperature. Plot Resistance versus Temperature for Cu and for Silicon.
Q.26 Three charges Q , Q and – Q are placed on the vertices of an equilateral triangle of side L. Find the net force experienced by the charge Q and the net force experienced by the charge – Q.
Q.27 Cell A has an emf EA and internal resistance rA while cell B has emf EB and internal
resistance rB. Derive an expression for the equivalent emf and internal resistance
Q.28 What are coherent sources ? why are coherent sources required to produced interference of light ? give an example of interference of light in everyday life .in youngs double slit experiment , the two slit are 0.03 cm apart and the screen is placed at a distance of 1.5m away from the slit. The distance between the central bright fringe and fourth bright fringe is 1 cm apart. Calculate the wavelength of light used?
Draw a labeled ray diagram of compound microscope, in the normal adjustment position and write the expression for its magnifying power
The focal length of objective and eye lenses of a compound microscope are 2 cm ,6.25 cm resp.the distance between lenses is 15 cm .(1)How far from the objective lens will the object be kept so as to obtain the final image and the near point of the eye?(ii)also calculate its magnifying power?
Q.29 With the help of suitable diagram explain PNP CB amplifier and what is the phase difference between input and out wave form.
Q.30 (i) Explain with the help of a labeled Diagram, the principle, construction and working of an a.c. generator ?Deduce the expression for the e.m.f generated?
(ii) An ac generator consist of coil of 50 turns and area 2.5 m sq. rotating at an angular speed of 60 rad /s in a uniform magnetic field B= 0.30 T BETWEEN TWO FIXED POLE PIECES . the resistance of the circuit including that of the coil is 500Ω
find the maximum current drawn from the generator ?