RBSE Class 12 Physics Model Paper 4 English Medium

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RBSE Class 12 Physics Model Paper 4 English Medium are part of RBSE Class 12 Physics Board Model Papers. Here we have given RBSE Class 12 Physics Sample Paper 4 English Medium.

Board RBSE
Textbook SIERT, Rajasthan
Class Class 12
Subject Physics
Paper Set Model Paper 4
Category RBSE Model Papers

RBSE Class 12 Physics Sample Paper 4 English Medium

Time : 3 ¼ hours
Total: 56

General Instructions to the Examinees

  1. Candidate must first his/her Roll No. on the question paper compulsorily.
  2. All the questions are compulsory.
  3. Write the answer to each question in the given answer-book only.
  4. For questions having more than one part, the answer to those parts are to be written together in continuity.
  5. If there is any error/difference/contradiction in Hindi & English version of the question
    paper, the question of Hindi version should be treated valid.
  6. Question Nos Marks per Questions
    1-13 1
    14-24 2
    25-27 3
    28-30 4
  7. There are internal choices in Q. NOs. 21 and 27 to 30.
  8. Use of calculator is not allowed in the examination.

Section – A

Question 1.
Where does a capacitor store its energy? [1]

Question 2.
State two factors on which the internal resistance of a cell depends. [1]

Question 3.
An electron is moving north-ward in a magnetic field directed vertically downward. In which direction will the electron experience the force? [1]

RBSE Class 12 Physics Model Paper 4 English Medium

Question 4.
What is the locus of a charged particle when projected parallel to an electric field but perpendicular to a simultaneous magnetic field? [1]

Question 5.
If the horizontal and vertical component of earth’s magnetic field are equal at a place, find the angle of dip. [1]

Question 6.
Two similar circular co-axial loops carry equal currents in the same direction. If the loops are brought near, what will happen to the currents in them? [1]

Question 7.
What is total internal reflection? [1]

Question 8.
Write de-Broglie’s equation. [1]

RBSE Class 12 Physics Model Paper 4 English Medium

Question 9.
Show. that the wavelength of electromagnetic radiation equal to the de-Broglie wavelength of its quantum (photon). [1]

Question 10.
Half life of carbon is 5600 years. What is its average life? [1]

Question 11.
Why is the base region of a transistor made very thin and lightly doped? [1]

Question 12.
State two important features of amplitude modulation. [1]

Question 13.
What does the term LOS communication mean? Name the type of waves that are used for their communication? Which of the two: height of transmitting antenna or the height of receiving antenna or both can effect , the range over which this made of transmission is made? [1]

Section – B

Question 14.
Two charges +50μC and +20μC are 1m apart in vacuum. Find the work done in bringing them 40cm closer. [2]

RBSE Class 12 Physics Model Paper 4 English Medium

Question 15.
Derive expressions for equivalent emf and internal resistance in case of parallel grouping of cells. [2]

Question 16.
Find the equivalent resistance between X and Y of the given circuit. [2]
RBSE Class 12 Physics Model Paper 4 English Medium 1

Question 17.
A magnetic dipole is placed in a uniform magnetic field with its axis tilted with respect to its position of stable equilibrium. Derive an expression for its time period of oscillation about an axis passing through its centre and perpendicular to its plane. [2]

Question 18.
In a step down transformer turns ratio is 20:1 having input voltage 220V and output current is 8A. Assuming 100% efficiency calculate voltage across second coil, current in primary coil and power output. [2]

Question 19.
State the condition for diffraction of light to occur. In the diffraction at a single slit experiment, how would the width and the intensity of central maximum change if  [2]

  1. Slit width is halved and
  2. Visible light of longer wavelength is used?

RBSE Class 12 Physics Model Paper 4 English Medium

Question 20.
A compound microscope uses an objective lens of focal length 4cm and eye lens of focal length 10cm. An object is placed at 6cm from the objective lens. Calculate the magnifying power of the compound microscope if the final image is formed at near point. [2]

Question 21.
The wavelength of light falling on a photo sensitive surface is changed from 2000Å to 2100Å. What is the corresponding change in stopping potential? [2]

Question 22.
Calculate  [2]

  1. the shortest and
  2. the longest wavelengths of Lyman series (R = 10967700m-1)

OR
(a) What percentage of a given mass of a radioactive substance will be left undecayed after five half life periods?
(b) A radioactive substance decays to \(\frac { 1 }{ 32 } \) of its initial activity in 25 days. Calculate its half life.

Question 23.
Describe briefly with the help of a circuit diagram how is the flow of current carrier in a PNP transistor is regulated with emitter-base junction forward biased and collector -base junction reverse biased. [2]

Question 24.
State the properties of electromagnetic waves. [2]

Section – C

Question 25.
(a) Define decay rate or activity of a substance. Show that the decay rate R of radioactive sample is related to the number of radioactive nuclei N at the some instant by the expression R = λN. [3]
(b) Calculate half life of 238U if 1 g of uranium emits 1.23 x 104 a-particles per second.

RBSE Class 12 Physics Model Paper 4 English Medium

Question 26.
What is NOT gate? Give the Boolean expression, logic symbol and truth table for a NOT gate. Explain with the help of circuit diagram, how is this gate realised in practice. [3]

Question 27.
Define current sensitivity of a moving coil galvanometer and derive an expression for it. How can you increase the current sensitivity? [3]
OR
State Ampere’s law, Apply it to find magnetic field on the axis of a Toroid.

Section – D

Question 28.
(a) Define electric flux. How the flux is expressed in terms of surface integral of the electric field.  [4]
(b) Using Gauss’s law, find electric field intensity due to uniformly charged non-conducting sphere.
(c) Draw the graph showing variation of E with r.
OR
(a) What is the potential energy of a system of three charges q, q, and -q placed at the corners of an equilateral triangle of side a?
(b) Derive an expression for electric potential due to a charged spherical shell at an external point and hence on its surface.
(c) Two protons each having a speed of 106 ms-1 are far apart and approach each other. What will be the closest distance between them?

Question 29.
(a) Write one merit and one demerit of alternating current over direct current. Obtain expressions for  [4]

  1. instantaneous value of current,
  2. reactance of the circuit and
  3. peak value of current in a purely inductive circuit. (c) Draw curve for variation of power with time in pure inductive circuit.

OR
(a) Define inductive reactance and write an expression for it.
(b) Obtain an expression for magnetic potential energy in an inductor.
(c) Why choke is preferred to rheostat in controlling AC.

Question 30.
(a) By stating the sign convention and assumptions made derive thin lens formula for a double convex lens forming virtual image.
(b) The image obtained with a convex lens is erect and its length is four times the length of the object. If the focal length of the lens is 20cm, calculate the object and image distance. [4]

RBSE Class 12 Physics Model Paper 4 English Medium
OR
(a) What is diffraction? Distinguish between diffraction and interference.
(b) Using Huygen’s principle, explain diffraction of light due to a single slit and explain the formation of the pattern of the fringes obtained on the screen.
(c) Why backward movement of secondary wavelets is not possible?

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