# ISC Physics 2017 Class-12 Solved Previous Year Question Paper

**ISC Physics 2017 Class-12** Solved Previous Year Question Paper for practice. Step by step Solutions of Part I and II with section-A, B, C. Visit official website **CISCE **for detail information about **ISC Class-12 Physics**.

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### Previous Year Question Paper ISC Physics 2017 Class-12 Solved

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### Class-12 Solved Previous Year Question Paper ISC Physics 2017\

Maximum Marks: 70

Time allowed: Three hours

- Candidates are allowed additional 15 minutes for only reading the paper. They must NOT start writing during this time
- Answer all questions in Part I and ten questions from Part II, choosing four questions from
- Section A, three questions from Section B and three questions from Section C.
- All working, including rough work, should be done on the same sheet as, and adjacent to, the rest of the answer.
- The intended marks for questions or parts of questions are given in brackets [ ].
- Material to be supplied: Long tables including Trigonometric functions.
- A list of useful physical constants is given at the end of this paper.

### Part – I (20 Marks)

(Answer all questions)

( ISC Physics 2017 Class-12 Solved Previous Year Question Paper )

Question 1.

(a) Choose the correct alternative (a), (b), (c) or (d) for each of the questions given below: [5]
**(i) The electrostatic potential energy of two point charges, 1 μC each, placed 1 metre apart in air is :**

(a) 9 x 10^{3} J

(b) P x 10^{9 }J

(c) 9 x 10^{-3}J

(d) 9 x 10^{-3} eV

**(ii) A wire of resistance R ’ is cut into ‘n ’ equal parts. These parts are then connected in parallel with each other. The equivalent resistance of the combination is :**

(a) nR

(b) R/n

(c) n/R^{2}

(d) R/n^{2}

**(iii) Magnetic susceptibility of platinum is 0.0001. Its relative permeability is :**

(a) 1.0000

(b) 0.9999

(c) 1.0001

(d) 0

**(iv) When a light wave travels from air to glass :**

(a) its wavelength decreases

(b) its wavelength increases

(c) there is no change in wavelength

(d) its frequency decreases.

**(v) A radioactive substance decays to 1/16th of its initial mass in 40 days. The half life of the substance, in days, is:**

(a) 20

(b) 10

(c) 5

(d) 2.5

**B. Answer all questions given below briefly and to the point: [15]**

(i) Maximum torque acting on the electric dipole of moment 3 × 10^{-29} Cm in a uniform electric field E is 6 × 10^{-25} Nm. Find E.

(ii) What is meant by drift speed of free electrons ?

(iii) On which conservation principle is Kirchhoff’s Second Law of electrical networks based ?

(iv) Calculate magnetic flux density of the magnetic field at the center of a circular coil of 50 turns, having radius of 0.5 m and carrying a current of 5 A. .

(v) An a.c. generator generates an emf ‘s’ where e = 314 Sin (50 πt) volt. Calculate the frequency of the emf ∈.

(vi) With what type of source of light are cylindrical wave fronts associated ?

(vii) How is fringe width of an interference pattern in Young’s double slit experiment affected if the two slits are brought closer to each other ?

(viii) In a regular prism, what is the relation between angle of incidence and angle of emergence when it is in the minimum deviation position ?

(ix) A converging lens of focal length 40 cm is kept in contact with a diverging lens of focal length 30 cm. Find the focal length of the combination.

(x) How can the spherical aberration produced by a lens be minimised ?

(xi) Calculate the momentum of a photon of energy 6 x 10^{-19} J.

(xii) According to Bohr, Angular momentum of an orbiting electron is quantised. ’ What is meant by this statement ?

(xiii) Why nuclear fusion reaction is also called thermo-nuclear reaction ?

(xiv) What is the minimum energy which a gamma ray photon must possess in order to produce electron-positron pair ?

(xv) Show the variation of voltage with time, for a digital signal.

Answers:

Section-A Part – II (20 Marks)

(Answer any four questions)

**Answer ten questions in this part, choosing four questions from Section A, three questions from Section B and three questions from Section C**

### ( ISC Physics 2017 Class-12 Solved Previous Year Question Paper )

Question 2.

(a) Show that electric potential at a point P, at a distance ‘r’ from a fixed point charge Q, is given by: [4]

(b) Intensity of electric field at a perpendicular distance of 0.5 m from an infinitely long line charge having linear charge density (X) is 3.6 x 10^{3} Vm^{-1}. Find the value of λ . [1]
Answer:

Question 3.

**(a) Three capacitors C _{1} = 3 μF, C_{1} = 6 μF and C_{1}= 10 μF are connected to a 50 V battery as shown in the Figure 1 below : [3]**

**Calculate**:

(i) The equivalent capacitance of the circuit between points A and B.

(ii) The charge on C

_{1}

(b) Two resistors R

_{1}= 60 Ω and R

_{2}90 Ω are connected in parallel .If electric power consumed by the resistor R

_{1}is 15 W, calculate the power consumed by the resistor R

_{2}. [2] Answer:

a) C

_{1}= 3 μF1, C

_{2}= 6 μF, C

_{3}= 10 μF

If C’ be in equivalent capacitance between C

_{1}and C

_{2}, then

Question 4.

(a) Figure 2 below shows two resistors R

_{1}and R

_{2}connected to a battery having an emf of 40 V and negligible internal resistance. A voltmeter having a resistance of 300 Ω is used to measure potential difference across R

_{1}. Find the reading of the voltmeter. [3]

(b) A moving coil galvanometer has a coil of resistance 59 Ω. It shows a full scale deflection for a current of 50 mA. How will you convert it to an ammeter having a range of 0 to 3A ? [2] Answer:

Question 5.

(a) In a meter bridge circuit, resistance in the left hand gap is 2 Ω and an unknown resistance X is in the right hand gap as shown in Figure 3 below. The null point is found to be 40 cm from the left end of the wire. What resistance should be connected to X so that the new null point is 50 cm from the left end of the wire ?

b) The horizontal component of earth’s magnetic field at a place is 1/√3 times the vertical component. Determine the angle of dip at that place.

Answer:

Question 6.

(a) Using Ampere’s circuital law, obtain an expression for the magnetic flux density ‘B’ at a point X’at a perpendicular distance ‘r from a long current carrying conductor. (Statement of the law is not required). [3]
(b) PQ is a long straight conductor carrying a current of 3A as shown in Figure 4 below. An electron moves with a velocity of 2 × 10^{7} ms^{-1} parallel to it. Find the force acting on the electron.

Answer:

Question 7.

(a) (i) AB and CD are two parallel conductors kept 1 m apart and connected by a resistance R of 6 Ω as shown in Figure 5 below. They are placed in a magnetic field B = 3 × 10^{-2} T which is perpendicular to the plane of the conductors and directed into the paper. A wire MN is placed over AB and CD and then made to slide with a velocity 2 ms-l. (Neglect the resistance of AB, CD. and MN). [3]

Calculate the induced current flowing through the resistor R.

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