Archive for the ‘Class XII Guess papers’ Category

CBSE Guess paper class XII PHYSICS 2008 1

May 22, 2008


Guess Paper – 2008

Class – XII

Subject – Physics


CLASS-XII SUB-PHYSICS MAX MARKS-60

DATE- TIME-3hrs.

GENERAL INSTRUCTIONS.

1. All questions are compulsory.

2. There is no overall choice. How ever, an internal choice has been given provided in one question of 2 marks, one question of 3 marks, and three questions of five marks.

3. Question numbers 1-8 are very short answer type questions, carrying 1 mark each.

4. Question numbers 9-18 are short answer type questions, carrying 2 marks each.

5. Question numbers 19-27 are short answer type questions, carrying 3 marks each.

6. Question numbers 28-30 are long answer type questions, carrying 5 marks each.

7. Calculators are not allowed. However you may use log tables if necessary.

C = 3 x 10 8 m/s

h = 6.6 x 10 –34 Js

e = 1.6 x 10 –19 C

μ0 = 4 x 10 –7 TmA –1

1. Consider the situation of the two poles P and Q shown in the figure below. What are the signs of P and Q?

p

Q

2. The polarizing angle of a medium is 600. What is the refractive index of the medium?

3. Name 2 materials, which are used for making standard resistance coils.

4. Lorentz force is given by F = I (LxB). Of these, name the pairs of vectors which are always at right angles to each other.

  1. What is the power factor of an LCR circuit at resonance?

6. An inductor of 10mH carries a current of 2A. The current is increased to 5A in 10 seconds. What is the voltage induced in the inductor?

7. Compare the radii of two nuclei with mass number 1 and 27 respectively.

8. Define Attenuation.

9. A charge of 5C is placed at the origin and –10C is placed at the point x = 30. Find a point on the x axis at which (a) Electric field is zero (b) Potential is zero.

10. What are electric field lines? Mention 2 properties.

11. Name the elements of earth’s magnetism.

  1. How can one distinguish between on unpolarised light beam and a linearly polarized light beam using a Polaroid?
  2. The photoelectric cut-off voltage in a certain experiment is 1.5 V. What is the maximum K.E. of photoelectrons emitted?
  3. Explain the effect of potential on photoelectric current and draw the graph for different intensities.
  4. Obtain the binding energy (in MeV) of a nitrogen nucleus ( 147N ), given mass of N = 14.00307 u.
  5. The input of a 2-input NAND gate is fed to a Not gate, write down the truth table for the combination for all possible inputs of A and B.


17. A communication system mainly consists of three major parts. Name them. Draw the block diagram of a generalized communication system.

  1. A transmitting antenna at the top of a tower has a height 32 m and the height of the receiving antenna is 50 m.What is the maximum distance between them for satisfactory communication in LOS mode? Given radius of the earth is 6.4 x 106 m.
  2. The electrostatic force on a small sphere of charge 4C due to another small sphere of charge 8C in air is F. What is the distance b/w the 2 spheres. What is the force on the –8C sphere due to the first sphere. What will the force be if the spheres are dipped in a liquid having dielectric constant K.
  3. Deduce the condition for balance in a Wheatstone bridge. Using the principle of Wheatstone Bridge, describe the method to determine the specific resistance of a wire in the laboratory. Draw the circuit diagram and write the formula used.

21. A resistance has color coding as ( green, red, brown,) and other one has (blue, black, grey).

Find the ratio of power dissipated in first to the power dissipated in second if both are separately connected across 220V-power supply.

  1. Draw the ray diagram showing the formation of image of an object using a compound microscope?
  2. A converging lens has a focal length of 200m in air it is made of a material of refractive index 1.6 If it is immersed in a liquid of refractive index 1.3 what will be its new focal length?

24. When an inductor L and a resistance R in series are connected across a 12 V , 50Hz ac source, a current of 0.5A flows in the circuit. The current differs in phase from applied voltage by π/3 radian. Calculate the value of R.

25. Briefly explain the construction and working of a transformer. Mention 3 factors responsible for the decrease in efficiency.

26.With a schematic arrangement of the Geiger-Marsden experiment, explain α-particle scattering.

27. Write short notes on

(1) Microwaves

(2) X-Rays

28. What is Hysterisis? Draw the hysterisis loops for soft iron and steel. Explain Retentivity and Coercivity. Hence explain which material you would prefer for making

1) Permanent magnet

2) Core of a transformer

3) Electromagnet

Or

Explain the construction and working of a moving coil galvanometer. A moving coil galvanometer is made of a coil of radius 10cm and has 1000 turns. The strong horse shoe magnets create a magnetic field of 0.2T and the spring has a spring constant of 0.5 N/m. Find the

1) Galvanometer constant G

2) Current sensitivity Is

3) Voltage Sensitivity Vs

Explain how a galvanometer can be made more sensitive?

29. Define principle of superposition. Drive the expression for the fringe width in young’s double slit interference experiment? Write two conditions for interference. What is the difference between interference pattern and diffraction pattern?

Or

State the postulates of Huygens wave theory. Prove laws of reflection and refraction using Huygens wave theory.

30. Draw a labelled diagram of transistor oscillator. Briefly explain its principle and state how the oscillation is sustained?

Or

Draw the energy band diagrams of p –type and n- type semi-conductors. Explain with a circuit diagram the working of a full wave rectifier

CBSE Guess paper class XII Physics 2008 2

May 22, 2008

Guess Paper – 2008

Class – XII

Subject – Physics

( Based on the new pattern of CBSE board examination 2008 )

EMI and AC

( NCERT units 6 and 7 )

Time Allowed : 3 hours Maximum Marks : 70

(a) All questions are compulsory

(b) Question numbers 1 to 8 are very short answer type questions, carrying one mark each.

(c) Question numbers 9 to 18 are short answer type questions, carrying two marks each.

(d) Question numbers 19 to 27 carry three marks each.

(e) Question numbers 28 to 30 are long answer type questions, carrying five marks each.

(f) Use of calculators is not permitted. However, you may use log tables, if necessary.

Q.1> Define Alternating current and mention its SI unit

Q.2> Name the element in which current leads voltage by 90 degrees.

Q.3> What is the power factor of an LCR circuit at resonance?

Q.4> An inductor of 10mH carries a current of 2A. The current is increased to 5A in 10 seconds. What is the voltage induced in the inductor?

Q.5> Name the phenomenon associated with the production of back emf in a coil due to change in the current in the coil itself. What is the SI unit for measuring this characteristic?

Q.6> What is electro magnetic induction?

Q.7> A 100 ohm resistor is connected to a 200 volt, 50 Hz power supply. What is the net power loss In the resistance.

Q.8> A bulb is connected in series with a capacitor to a DC source. Explain what will happen.

Q.9> Why is choke coil needed in the use of fluorescent tubes with ac mains? Why can we not use an ordinary resistor instead of the choke coil?

Q.10> Can we use an ordinary ammeter to measure alternating current? If not, explain why.

Q.11>If in an LCR circuit, the frequency of the supply is doubled, how should the values of C and L be changed so as to keep the current in the circuit constant.

Q.12> An ideal transformer is supplied with 10KW power at 200 volts. Find the output voltage and current if the transformation ratio is 5.

Q.13> State Faraday’s law of electromagnetic induction.

Q.14> A coil of area 2m2 is placed in a magnetic field B(t) = 4t + 3 Tesla. The resistance of the coil is 100 milliOhm. Find the induced current in the coil.

Q.15> Give one line definitions for the following

(a) Resistance (b) Reactance (c) Impedance

Q.16> Draw a graph showing the variation of Impedance of an LCR circuit as a function of source frequency. Also plot current on the same graph and hence define resonance frequency.

Q.17> An aeroplane with a wingspan of 50m is flying with a speed of 1Km/sec. The magnetic field of earth at that place is 300 G at a dip angle of 30 degrees, Find the induced emf across the plane.

Q.18> An inward magnetic field exists in a region, Find the direction of induced current if

(a) a square loop ( lying outside the field ) is being pushed into the magnetic field region.

(b) A circular coil ( lying inside the field ) is pulled out of the magnetic field.

(c) A triangular loop is moved inside the magnetic field.

Q.19> Show that the net power loss in an ideal inductor is zero.

(b) The power factor of an ac circuit is 0.5. What is the phase difference b/w voltage and current?

Q.20> State Lenz law and show that it obeys energy conservation

Q.21> What are eddy currents? Explain a method to reduce them. Also mention 2 applications.

Q.22> Derive an expression for the mutual inductance of a pair of solenoids, where the smaller one is placed completely inside the bigger one.

Q.23> An AC source given by E = Eosinωt is connected across a capacitor. Derive an expression for the current flowing in the circuit and plot the phasor diagram.

Q.24> On a graph plot the variation of voltage and current versus ωt for the case of

(a) Pure resistor

(b) Pure inductor

(c) Pure capacitor

Q.25> What is the principle of working of an ac generator? The armature of an AC generator has 1000 turns of 1m2 area. Its strong horse shoe magnets produce a magnetic field of 0.25T. The armature is connected to a windmill due to which it rotates at 5 revolutions per minute. Find the maximum, average and the rms voltage produced by this generator.

Q.26> A 400mH inductor and a 3 ohm resistor are connected in series to a 500 volt , 5 / π Hz source. Find the peak current and the phase difference b/w the V and I. Also draw the impedance triangle.

Q.27> If the frequency of ac is increased then what will be the effect on current in case of following a.c. circuits. Give reasons

(1) Resistance circuit

(2) Inductor circuit

(3) Capacitor circuit

Q.28> Briefly explain the construction and working of a transformer. Mention 3 factors responsible for the decrease in efficiency.

Q.29> A series LCR circuit is connected to variable frequency 220 volt source. L = 5H, C = 80microFarad and R = 20 ohms.

(a) Determine the source frequency, which drives the circuit in resonance.

(b) Obtain the impedance of the circuit and amplitude of current at resonance

(c) Find the potential drop across each of the 3 elements. Is the algebraic sum greater than the source voltage? If yes, resolve the paradox.

Q.30> When an inductor L and a resistance R in series are connected across a 12 V , 50Hz ac source, a current of 0.5A flows in the circuit. The current differs in phase from applied voltage by π/3 radian. Calculate the value of R.

(b) A capacitor and a bulb are connected in series to an ac source. Explain, how the brightness of the bulb will change when

(a) Distance b/w the plates of the capacitor is increased

(b) A dielectric slab is introduced in the capacitor

——————————————————————————————————

CBSE Guess paper class XII Mathematics 2008 3

May 22, 2008
Due to font error many are unable to see this paper therefore we are giving the paper to download.

Click here to download

CBSE Guess paper class XII Mathematics 2008 4

May 22, 2008
Due to font error many are unable to see this paper therefore we are giving the paper to download.

Click here to download

CBSE Guess paper class XII Mathematics 2008 2

May 22, 2008
Due to font error many are unable to see this paper therefore we are giving the paper to download.

Click here to download

CBSE Guess paper class XII Mathematics 2008 5

May 22, 2008

EGuess Paper – 2008

Class – XII

Subject – Mathematics

DIFFERENTIATION

1.

x2 sin xy + y cos x = 2

2.

(x2 + 2y)2 + x3 + y2 = 2x

3.

tan-1 _3x – 4_

1 + 12x

4.

tan-1 √(1 + a2x2) – 1

ax

5.

cos-1 3 + 5cosx

5+3cos x

6.

cos-1 1 – x2p

1 + x2p

7.

x2 sin3 x cos4 x

8.

log sinm x

cosn x

9.

log tan x – cot x log (1+sin x)

2

10.

__sin2x__ + __cos2x__

1 + cot x 1 + tan x

11.

If y = √x + 1/x, show that

2x dy/dx + y = 2√x

12.

If y = 1 + x + x2 + x3 +…+ xn

2! 3! n!

show that, dy + xn = y

dx n!

13.

If y = log 1 + tan x 1/2

1 – tan x

prove that dy/dx = sec 2x

14.

If yx + xy = K, show that

dy = – yx log y + yxy – 1

dx xy log x + xyx – 1

15.

If x + y = sin (x + y), show that dy/dx = – 1

16.

If ex+ y = xy, show that

dy/dx = y (1 – x)/x ( y – 1)

17.

If √(1–x4) + √(1–y4) = k (x2– y2)

s.t. y√(1–x4) dy/dx = x √(1–y4)

18.

If y= tan-1xn+tannx – tan-1 a+xn

1-axn

s.t.dy/dx = n tann-1x sec2x

19.

If x = a(cos θ + θ sin θ) and

y = a(sin θ – θ cos θ), show that, a θ d2y/dx2 = sec3 θ

20.

If y = sin-1 x/ √(1–x2), show that,

(1–x2)d2y/dx2 –3x dy/dx–y =0


SAM

CBSE Guess paper class XII Mathematics 2008 1

May 22, 2008

Guess Paper – 2008

Class – XII

Subject – Mathematics

1. Show that the vector i+j+k is equally inclined with the positive directions of the coordinate axes.

2. Find unit vector perpendicular to each of the vectors 2i-j+k and i+j+k.

3. Examine whether points with position vectors -2i+3j+5k,i+2j+3k,7i-k are collinear.

4. Find distance of point(2,-1,3) from the plane r.(5i+2j-7k)+12=0.

5. Find equation of plane passing through points (1,0,2),(-1,3,2),(2,1,5).

6. Find the vector equation of the plane passing through intersection of the planes r.(i+2j+3k)=4 and r.(2i+j-k)+5=0 and which is perpendicular to the plane r.(5i+3j-6k)+8=0.

7. If a,b,c are position vectors of non-collinear points A,B,C respectively in space , show that bxc+cxa+axb is perpendicular to the plane ABC.

8. Find shortest distance between the lines r=3i+8j+3k+ג (3i-j+k) and r=-3i-7j+6k+µ (-3i+2j+4k).

9. Find foot of perpendicular drawn from the point (1,3,4) on the plane r.(2i-j+k)+3=0.

10. Minimize Z=3x+5y subject to the constraints

x-4y+12≥0, 2x+3y-12≥0, x≤4, y≥2, x≥0.

11. Show that the points with position vectors a-2b+3c,-2a+3b+2c and -8a+13b are collinear.

12. Find area of triangle whose vertices are (3,-1,2),(1,-1,-3),(4,-3,1).

13.A variable plane is at a constant distance p from the origin ,cuts the coordinate axes in A,B,C.Through A,B,C planes are drawn parallel to coordinate planes . Show that the locus of their point of intersection is x-2 + y-2 + z-2 = p-2.

14.Show that the points(0,-1,-1),(-4,4,4),(4,5,1),and (3,9,4) are coplanar also find equation of the plane.

15.Find equation of line joining (3,4,1) and point of intersection of the line r=3i+ ג (i-j) and the plane r.(3i+j)-9=0.

16.Find the distance of the point (2,3,4) from the plane 3x + 2y +2z +5=0 measured parallel to the line

( X+3)/3 = (y-2)/6=z/2

17.Kellogg is a new cereal formed by a mixture of bran and rice that contains at least 88 grams of protein and at least 36 miligram of iron .Knowing that bran contains 80 grams of protein and 40 miligrams of iron per kilogram,and that rice contains 100 grams of protein and 30 miligram of iron per kilogram. Find minimum cost of producing this new cereal if bran costs Rs. 5 per kilogram and rice costs Rs. 4 per kilogram.


Follow

Get every new post delivered to your Inbox.

Join 38 other followers