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CBSE Class 12 Physics Last 5 + 1 Years’ Long Answer Type Questions

Jan 18, 2017 12:10 IST

    CBSE class 12 Physics previous 5 + 1 years’ long answer type questions are available in this article.

    According to the latest examination pattern, there will be 12 long answer type questions (or 3 marks questions) will be asked in CBSE class 12 Physics board exam 2017. But, before the year 2015, the examination pattern of CBSE Class 12 Physics board exam was quite different. However, in order to understand the level of questions which can be asked in CBSE class 12 Physics exam 2017, students of CBSE class 12 must go through these questions.

    CBSE Class 12 Physics Sample Paper 2017

    Students can also find the solutions of these questions in CBSE Class 12th Solved Previous Years' Papers (Last 5+ 1 years') PCM - eBook

    The questions are give below:

    CBSE Class 12 Physics Board Exam 2016: Long Answer Type Questions (3 Marks)

    Q. For a CE-transistor amplifier, the audio signal voltage across the collector resistance of 2 kΩ is 2 V. Suppose the current amplification factor of the transistor is 100, find the input signal voltage and base current, if the base resistance is 1 kΩ.

    CBSE Class 12 Physics Last 5 + 1 Years’ Short Answer Type Questions

    Q. (i) State law of Malus.

    (ii) Draw a graph showing the variation of intensity (I) of polarised light transmitted by an analyser with angle (θ) between polariser and analyser.

    (iii) What is the value of refractive index of a medium of polarising angle 60?

    CBSE Class 12 Physics Last 5 + 1 Years’ Very Short Answer Type Questions

    Q. (i) Which mode of propagation is used by shortwave broadcast services having frequency range from a few MHz upto 30 MHz? Explain diagrammatically how long distance communication can be achieved by this mode.

    (ii) Why is there an upper limit to frequency of waves used in this mode?

    Q. Sketch the graphs showing variation of stopping potential with frequency of incident radiations for two photosensitive materials A and B having threshold frequencies vA>vB.

    (i) In which case is the stopping potential more and why?

    (ii) Does the slope of the graph depend on the nature of the material used?

    CBSE Class 12 Syllabus 2017

    Q. (i) When an AC source is connected to an ideal inductor show that the average power supplied by the source over a complete cycle is zero.

    (ii) A lamp is connected in series with an inductor and an AC source. What happens to the brightness of the lamp when the key is plugged in and an iron rod is inserted inside the inductor? Explain.

      CBSE Class 12 Physics Board Exam 2016: Diagram of Long Answer Type Questions 3 Marks

    Q. (i) Explain with the help of a diagram the formation of depletion region and barrier potential in a p-n junction.

    (ii) Draw the circuit diagram of a half wave rectifier and explain its working.

    Q. (i) Identify the part of the electromagnetic spectrum which is:

    (a) suitable for radar system used in aircraft navigation,

    (b) produced by bombarding a metal target by high speed electrons.

    (ii) Why does a galvanometer show a momentary deflection at the time of charging or discharging a capacitor? Write the necessary expression to explain this observation.

    Q. Define the term wave front. State Huygens’s principle.

    Consider a plane wave front incident on a thin convex lens. Draw a proper diagram to show how the incident wave front traverses through the lens and after refraction focuses on the focal point of the lens, giving the shape of the emergent wave front.

    OR

    Q. Explain the following, giving reasons:

    (i) When monochromatic light is incident on a surface separating two media, the reflected and refracted light both have the same frequency as the incident frequency.

    (ii) When light travels from a rarer to a denser medium, the speed decreases.

    Does this decrease in speed imply a reduction in the energy carried by the wave?

    (iii) In the wave picture of light, intensity of light is determined by the square of the amplitude of the wave. What determines the intensity in the photon picture of light?

    Q. (a) Write the basic nuclear process involved in the emission of β+ in a symbolic form, by a radioactive nucleus.

    (b) In the reactions given below:

    CBSE Class 12 Physics Board Exam 2016: Diagram of Long Answer Type Questions 3 Marks based on Nuclear Reaction

    Find the values of x, y, and z and a, b and c.

    Q. Use Biot-Savart law to derive the expression for the magnetic field on the axis of a current carrying circular loop of radius R.

    Draw the magnetic field lines due to a circular wire carrying current I.

    Q. (i) Derive an expression for drift velocity of free electrons.

    (ii) How does drift velocity of electrons in a metallic conductor vary with increase in temperature? Explain.

    Q. Define an equipotential surface. Draw equipotential surfaces:

    (i) in the case of a single point charge and

    (ii) in a constant electric field in Z-direction. Why the equipotential surfaces about a single charge are not equidistant?

    (iii) Can electric field exist tangential to an equipotential surface? Give reason.

    CBSE Class 12 NCERT Solutions

    CBSE Class 12 Physics Board Exam 2015: Long Answer Type Questions (3 Marks)

    Q. Plot a graph showing the variation of current density (j) versus the electric field (E) for two conductors of different materials. What information from this plot regarding the properties of the conducting material, can be obtained which can be used to select suitable materials for use in making (i) standard resistance and (ii) connecting wires in electric circuits? Electron drift speed is estimated to be of the order of mm s−1. Yet large current of the order of few amperes can be set up in the wire. Explain briefly.

    Q. State Biot - Savart law. Deduce the expression for the magnetic field at a point on the axis of a current carrying circular loop of radius ‘R’ distant ‘x’ from the centre. Hence, write the magnetic field at the centre of a loop.

    Q. What does a polaroid consist of? Show using a simple polaroid, that light waves are transverse in nature. Intensity of light coming out of a polaroid does not change irrespective of the orientation of the pass axis of the polaroid. Explain why.

    Q. How is a Zener diode fabricated? What causes the setting up of high electric field even for small reverse bias voltage across the diode? Describe, with the help of a circuit diagram, the working of Zener diode as a voltage regulator.

    OR

    (a) Explain with the help of a diagram, how depletion region and potential barrier are formed in a junction diode.

    (b) If a small voltage is applied to a p-n junction diode, how will the barrier potential be affected when it is (i) forward biased, and (ii) reveres biased? 

    Q. Light of intensity ‘I’ and frequency ‘n ’ is incident on a photosensitive surface and causes photoelectric emission. What will be the effect on anode current when (i) the intensity of light is gradually increased, (ii) the frequency of incident radiation is increased, and (iii) the anode potential is increased? In each case, all other factors remain the same. Explain, giving justification in each case.

    Q. When is a transistor said to be in active state? Draw a circuit diagram of a p-n-p transistor and explain how it works as a transistor amplifier. Write clearly, why in the case of a transistor (i) the base is thin and lightly doped and (ii) the emitter is heavily doped.

    Q. (a) State three important factors showing the need for translating a low frequency signal into a high frequency wave before transmission.

    (b) Draw a sketch of a sinusoidal carrier wave along with a modulating signal and show how these are superimposed to obtain the resultant amplitude modulated wave.

    Q. You are given three circuit elements X, Y and Z. When the element X is connected across an AC source of a given voltage, the current and the voltage are in the same phase. When the element Y is connected in series with X across the source, voltage is ahead of the current in phase by p/4. But the current is ahead of the voltage in phase by p/4 when Z is connected in series with X across the source. Identify the circuit elements X, Y and Z.

    When all the three elements are connected in series across the same source, determine the impedance of the circuit.

    Draw a plot of the current versus the frequency of applied source and mention the significance of this plot.

    Q. Write symbolically the nuclear β+ decay process of 11C6. Is the decayed product X an isotope or isobar of 11C6?

    Given the mass values m (11C6) = 11.011434 u and m (X) = 11.009305 u. Estimate the Q-value in this process.

    Q. An object is placed 15 cm in front of a convex lens of focal length 10 cm. Find the nature and position of the image formed. Where a concave mirror of radius of curvature 20 cm should be placed so that the final image is formed at the position of the object itself?

    Q. Arrange the following electromagnetic wave in the order of their increasing wavelength:

    (a) γ- rays

    (b) Microwaves

    (c) X-rays

    (d) Radio waves

    How are infra-red waves produced? What role dose infra-red radiation play in (i) maintain the Earth’s warmth and (ii) physical therapy?

    Q. Explain briefly the process of charging a parallel plate capacitor when it is connected across a d.c. battery.

    A capacitor of capacitance ‘C’ is charged to ‘V’ volts by a battery. After some time the battery is disconnected and the distance between the plates is doubled. Now a slab of dielectric constant, 1 < k < 2, is introduced to fill the space between the plates. How will the following be affected?

    (a) The electric field between the plates of the capacitor

    (b) The energy stored in the capacitor Justify your answer by writing the necessary expressions.

    CBSE Class 12 Physics Board Exam 2014: Long Answer Type Questions (3 Marks)

    Q. (a) Using the phenomenon of polarisation, show how the transverse nature of light can be demonstrated.
    (b) Two polaroids P1 and P2 are placed with their pass axes perpendicular to each other. An unpolarised light of intensity I0 is incident on P1. A third polaroid P3 is kept in between P1 and P2 such that its pass axis makes an angle of 30° with that of P1. Determine the intensity of light transmitted through P1, P2 and P3.

    Define the term 'mutual inductance' between the two coils. Obtain the expression for mutual inductance of a pair of long coaxial solenoids each of length l and radii r1 and r2 (r2 >> r1). Total numbers of turns in the two solenoids are N1 and N2, respectively.

    Q. Answer the following:

    (a) Why are the connections between the resistors in a meter bridge made of thick copper strips?

    (b) Why is it generally preferred to obtain the balance point in the middle of the meter bridge wire?

    (c) Which material is used for the meter bridge wire and why?

    OR

    A resistance of R Ω draws current from a potentiometer, as shown in the figure. The potentiometer has a total resistance Ro Ω. A voltage V is supplied to the potentiometer. Derive an expression for the voltage across R when the sliding contact is in the middle of the potentiometer.

    CBSE Class 12 Physics Board Exam 2014: Long Answer Type Question of 3 Marks

    Q. A convex lens of focal length 20 cm is placed coaxially with a convex mirror of radius of curvature 20 cm. The two are kept at 15 cm apart. A point object lies 60 cm in front of the convex lens. Draw a ray diagram to show the formation of the image by the combination. Determine the nature and position of the image formed.

    Q. A voltage V = V sin ωt is applied to a series LCR circuit. Derive the expression for the average power dissipated over a cycle.

    Under what condition (i) no power is dissipated even though the current flows through the circuit, (ii) maximum power is dissipated in the circuit?

    Q. Write any two distinguishing features between conductors, semiconductors and insulators on the basis of energy band diagrams.

    Q. For the past some time, Aarti had been observing some erratic body movement, unsteadiness and lack of coordination in the activities of her sister Radha, who also used to complain of severe headache occasionally. Aarti suggested to her parents to get a medical check-up of Radha. The doctor thoroughly examined Radha and diagnosed that she has a brain tumour.

    (a) What, according to you, are the values displayed by Aarti?

    (b) How can radioisotopes help a doctor to diagnose brain tumour?

    Q. Write two basic modes of communication. Explain the process of amplitude modulation. Draw a schematic sketch showing how amplitude modulated signal is obtained by superposing a modulating signal over a sinusoidal carrier wave.

    Q. An electron microscope uses electrons accelerated by a voltage of 50 kV. Determine the de-Broglie wavelength associated with the electrons. Taking other factors, such as numerical aperture etc. to be same, how does the resolving power of an electron microscope compare with that of an optical microscope which used yellow light?

    CBSE Class 12 Physics Board Exam 2013: Long Answer Type Questions (3 Marks)

    Q. (a) For a given AC I = Im sin ω t, show that the average power dissipated in a resistor R over a complete cycle is {(im)R}/2.

    (b) A light bulb is rated at 100 w for a 220V AC supply. Calculate the resistance of the bulb. ???

    Q. A rectangular conductor LMNO is placed in a uniform magnetic field of 0.5 T. The field is directed perpendicular to the plane of the conductor. When the arm MN of length of 20 cm is moved towards left with a velocity of 10 ms-d, calculate the EMF induced in the arms. Given the resistance of the arm to be 5Ω (Assuming that other arms are of negligible resistance) find the value of the current in the arm.

    CBSE Class 12 Physics Board Exam 2013, Short Answer Type Questions of 3 Marks based on EMI

    OR

    Q. A wheel with 8 metallic spokes each 50 cm long is rotated with a speed of 120 rev/min in a plane normal to the horizontal component of the earth’s magnetic field. The Earth’s magnetic field at the place is 0.4 G and the angle of dip is 60. Calculate the EMF induced between the axle and the rim of the wheel. How will the value of EMF be affected if the number of spokes were increased?

    Q. Define the current sensitivity of a galvanometer. Write its S.I unit. Figure shows two circuits each having a galvanometer and a battery of 3V.When the galvanometers in each arrangement do not show any deflection; obtain the ratio R1/R2.

    CBSE Class 12 Physics Board Exam 2013: Long Answer Type Question of 3 Marks based on ray optics

    Q. A wire AB is carrying a steady current of 12 A and is lying on the table. Another wire CD carrying 5A is held directly above AB at a height pg 1 mm. Find the mass per unit length of wire CD so that it remains suspended at its position when left free. Give the direction of the current flowing in CD with respect to that in AB. (take the value of g = 10 ms‒2 )

    Q. Draw V-I characteristics of a p-n junction diode. Answer the following questions, giving reasons :

    (a) Why is the current under reverse bias almost independent of the applied potential upto a critical voltage?

    (b) Why does the reverse current show a sudden increase as the critical voltage? Name any semiconductor device which operates under the reverse bias in the breakdown region.

    Q. Draw a labelled ray diagram of a refracting telescope. Define its magnifying power and write expression for it. Write two important limitations of a refracting telescope over a reflecting type telescope.

    Q. Write Einstein’s photoelectric equation and point out any two characteristics properties of photons on which this equation is based. Briefly explain the three observed features which can be explained by this equation.

    Q. Name the types of waves which are used for line of sight (LOS) communication. What is the range of their frequencies? A Transmitting antenna at the top of a tower has a height of 20m and the height of the receiving antenna is 45 m. Calculate the maximum distance between them for satisfactory communication in LOS mode. (Radius of the Earth = 6.4×106 m).

    Q. (a) What is linearly polarised light? Describe briefly using a diagram how sunlight is polarised.

    (b) Unpolarised light is incident on a Polaroid. How the intensity of would transmitted light change when the Polaroid is rotated?

    CBSE Class 12 Physics Board Exam 2012: Long Answer Type Questions (3 Marks)

    Q. Deduce the expression for the electrostatic energy stored in a capacitor of capacitance ‘C’ and having charge ‘Q’. How will the (i) energy stored and (ii) the electric field inside the capacitor be affected when it is completely filled with a dielectric material of dielectric constant ‘K’?

    Q. Calculate the value of the resistance R in the circuit shown in the figure so that the current in the circuit is 0.2 A. What would be the potential difference between points B and E?

    CBSE Class 12 Physics Board Exam 2012: Long Answer Type Question of 3 Marks

    Q. You are given three lenses L1, L2 and L3 each of focal length 20 cm. An object is kept at 40 cm infront of L1, as shown. The final real image is formed at the focus ‘I’ of L3. Find the separations between L1, L2 and L3.

    CBSE Class 12 Physics Board Exam 2012: Long Answer Type Question of 3 Marks based on ray optics

    Q. Define the terms (i) ‘cut-off voltage’ and (ii) ‘threshold frequency’ in relation to the phenomenon of photoelectric effect.

    Using Einstein's photoelectric equation shows how the cut-off voltage and threshold frequency for a given photosensitive material can be determined with the help of a suitable plot/graph.

    Q. A series LCR circuit is connected to an ac source. Using the phasor diagram, derive the expression for the impedance of the circuit. Plot a graph to show the variation of current with frequency of the source, explaining the nature of its variation.

    Q. Mention three different modes of propagation used in communication system Explain with the help of a diagram how long distance communication can be achieved by ionospheric reflection of radio waves.

    Q. Draw a plot of potential energy of a pair of nucleons as a function of their separations. Mark the regions where the nuclear force is (i) attractive and (ii) repulsive. Write any two characteristic features of nuclear forces.

    Q. In a Gieger-Marsden experiment, calculate the distance of closest approach to the nucleus of Z = 80, when a-particle of 8 MeV energy impinges on it before it comes momentarily to rest and reverses its direction. How will the distance of closest approach the affected when the kinetic energy of the a-particle is doubled?

    OR

    The ground state energy of hydrogen atom is –13.6 eV. If an electron makes a transition from an energy level –0.85 eV to –3.4 eV, calculate the wavelength of the spectral line emitted. To which series of hydrogen spectrum does this wavelength belong?

    Q. Define relaxation time of the free electrons drifting in a conductor. How is it related to the drift velocity of free electrons? Use this relation to deduce expression for the electrical resistivity of the material.

    CBSE Class 12 Physics Board Exam 2011: Long Answer Type Questions (3 Marks)

    Q. A convex lens made up of glass of refractive index 1.5 is dipped, in turn, in (i) a medium of refractive index 1.65, (ii) a medium of refractive index 1.33.

    (a) Will it behave as a converging or a diverging lens in the two cases?

    (b) How will its focal length change in the two media?

    Q. Draw a plot showing the variation of photoelectric current with collector plate potential for two different frequencies v1 > v2, of incident radiation having the same intensity. In which case will the stopping potential be higher? Justify your answer.

    Q. Write briefly any two factors which demonstrate the need for modulating a signal. Draw a suitable diagram to show amplitude modulation using a sinusoidal signal as the modulating signal?

    Use the mirror equation to show that:

    (a) An object placed between f and 2f of a concave mirror produces a real image beyond 2f.

    (b) A convex mirror always produces a virtual image independent of the location of the object.

    (c) An object placed between the pole and focus of a concave mirror produces a virtual and enlarged image.

    Q. Draw a labeled diagram of a full wave rectifier circuit. State its working principle. Show the input-output waveforms?

    Q. (a) Using de Broglie's hypothesis, explain with the help of a suitable diagram, Bohr's second postulate of quantization of energy levels in a hydrogen atom.

    (b) The ground state energy of hydrogen atom is ‒ 13.6 eV. What are the kinetic and potential energies of the electron in this state?

    Q. You are given a circuit below. Write its truth table. Hence, identify the logic operation carried out by this circuit. Draw the logic symbol of the gate it corresponds to?

    CBSE Class 12 Physics Board Exam 2011: Long Answer Type Questions of 3 Marks

    CBSE Class 12th Solved Previous Years' Papers (Last 5+ 1 years') PCM - eBook

    DISCLAIMER: JPL and its affiliates shall have no liability for any views, thoughts and comments expressed on this article.

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