Physics Classes

Category: 12th Assignments

  • Very important questions of ray optics

    Very important questions of ray optics

    Very important topics for ray optics
    Very important questions of ray optics-

    In this topic we will get some, Very important questions of ray optics. Students preparing for board examination must solve all the questions given below.

    Very important questions of ray optics

    1. Derive the mathematical relation between refractive indices μ1 and μ2 of two radii and radius of curvature R for refraction at a convex spherical surfaces. Consider the object to be a point source on the principle axis in rarer medium of refractive index  μ1 and a real image formed in the denser medium .

    Light from a point source in air falls on a convex spherical glass surface of refractive index 1.5 and radius of curvature 20 cm . The distance of light source from the glass surface is 100cm . At what position the image will be formed?

    2. A point object is placed in front of a double convex lens with its spherical faces of radii of curvature R1 and R2 . Show the path of rays due to refraction at first and subsequently at the second surface to obtain the formation of the real image of the object. Hence obtain the lens maker’s formula for a thin lens.

    (i)   A double convex lens having both faces of the same radius of curvature has refractive index 1.5. Find out the radius of curvature of the lens required to get the focal length of 20 cm . (ii) How the focal length of the above lens changes when it is placed in liquid of refractive index (a) 1.3 (b) 1.5 and (c)2.5 .

    To solve this questions students must watch this video

    3. Draw the ray diagram to show the refraction of a ray of monochromatic light passing through a glass prism. Deduce the expression for the refractive index of glass in terms of angle of prism and angle of minimum deviation.

    A ray of light incident on face AB of an equilateral glass prism ABC , shows minimum deviation of 300 calculate the speed of light through the prism. Also find the angle of incidence at face AB so that the emergent ray along the face AC .

    4.What do you mean by the term total internal reflection also write the conditions to get the total internal reflection, define the term critical angle for a pair of media , how the critical angle is related to the refractive index of the medium. A point source is kept at the bottom of the pond 2m deep ( μ= 4/3 )draw the ray diagram and calculate the area of water surface through which light emerges out of the pond.

    5. Draw a ray diagram showing the image formation of compound microscope, hence obtain the expression for magnifying power when (I) image is formed at infinity (II) image is formed at least distance of distinct vision. (a)Why must both the objective and eyepiece of a compound microscope have short wavelength? (b) while viewing through a compound microscope, why should our eyes be placed not on the eye piece but at short distance away from it for best viewing?

    TO WATCH THE COMPLETE VIDEO OF THIS TOPIC CLICK ON THE VIDEO GIVEN BELOW-

    6. Draw a labelled ray diagram of astronomical telescope, for(I) normal adjustment, (II) at least distance of distinct of vision. Also derive the expression for magnifying power .You are given the three lance L1 , L2 , L3 having power 3D , 6D and 10D respectively with aperture 8cm,1cm and 1cm respectively, which two lances will you use as an eyepiece and objective to construct (a) compound microscope and (b) Astronomical telescope. Give reasons.

    7.Explain reflecting type telescope draw the ray diagram for (I) Newtonian and (II)Cassegrainian type telescope. Write advantages of reflecting type telescope over refracting type telescope.

    8.Derive lens formula in a convex lens using suitable ray diagram 1/v -1/u = 1/f . (a) A convex les is used to obtain the image of an object on the screen 10 cm from the lens . if the magnification is 19, find the focal length of the lens. (b) An illuminated object and a screen are placed 90 cm apart. Determine the focal length and nature of the lens required to produce a clear image on the screen , twice the size of the object.

    TO WATCH THE COMPLETE VIDEO OF THIS TOPIC CLICK ON THE VIDEO GIVEN BELOW-

     

    Very important topics for ray optics
    Very important Short answer type questions of ray optics
  • Complete assignment of magnetic effect of current

    Complete assignment of magnetic effect of current

    Complete assignment of magnetic effect of current

    In this assignment Complete assignment of magnetic effect of current all kind of questions , objective , short answer type questions, long answer type questions and all kind of numericals with hots questions.

    Before to solve this assignment students must know the syllabus  and notes related to this chapter magnetic effect of current.

    After solving these questions students will be able to solve the all kind of questions related to this chapter. Specially objective type question will help the students to solve the questions for all competitive examinations like JEE and NEET along with board examinations.

    TO download complete assignment of magnetic effect of current click here-

    Some of the examples of Multiple choice – ( Answers of all the multiple type questions given below ; after the multiple type questions)

    1. Magnetic induction is measured in:
    • (a)weber (b) weber/m
    • (c) weber/m2    (d) weber/m3
    1. The force acting on a charge q moving with a velocity ʋ in a magnetic field of induction B is given by:
    • (a)q/(ʋ ₓ B)   (b) (ʋ ₓ B)/q
    • (c) q/(ʋ ₓ B)  (d) (ʋ . B)q
    1. Two free parallel wire carrying currents in the opposite directions:
    • (a) attract each other
    • (b) repel each other
    • (c) do not affect each other
    • (d) get rotated to be perpendicular to each other
    1. Two parallel wires carrying currents in the same direction attract each other because of:
    • (a) potential difference between them
    • (b) mutual inductance between them
    • (c) electric forces between them
    • (d) magnetic force between them
    1. A free charged particle moves through a magnetic field. The particle may undergo a change in:
    • (a)speed         (c) direction of motion
    • (b)energy       (d) none these

    To download complete assignment of Complete assignment click on the link given below-

    complete assignment of magnetic effect of current

     

     

     

  • Complete assignment of electric current

    Complete assignment of electric current

    Complete assignment of electric current –

    physics classes by Nayan jha already provided assignment of electric current . But this is the Complete assignment of electric current . In students  can solve all kind of questions like objective,fill in the blanks,very short, short , long answer type , numericals and hots questions . This assignment will help the students to prepare for 12th board and all kind of competitive examination like JEE and NEET .Specially the objective questions are very helpful for board and competitive examinations.

    Before to solve this assignment students must learn complete assignment of electric current .

    To download the notes of electric current click here-

    Some questions of this assignment is given here-

    1. For which of the following dependence of drift velocity ʋ on electric field E is ohm’s law obeyed?                                                          (a)ʋ ꭀ E    (b) ʋ = constant           (c) ʋ ꭀ E1/2           (d) ʋ ꭀ E2

    Ans-a

    1. in metals the time of relaxation of electrons:
    • (a)increases with increasing temperature
    • (b)decreases with increasing temperature
    • (c)does not depend on temperature
    • (d)changes suddenly at 400 K

    Ans-b

    1. Constantan wire is used for making standard resistance because it has:
    • (a)low specific resistance
    • (b)high specific resistance
    • (c)negligible temperature coefficient of resistance
    • (d)high melting point

    Ans-c

    1. A potential difference is applied across the ends of a metallic wire. If the potential difference is doubled, the drift velocity:
    • (a)will be doubled (c) will be quadrupled
    • (b)will be halved (d) will remain unchanged

    Ans-a

    1. The maximum current that flows in the fuse wire, before it blow out, varies with the radius r as:
    • (a)r3/2 (b) r   (c) r2/3   (d) r1/2

    Ans-a

    1. A wire of resistance R is cut into n equal parts. These parts are then connected in parallel. The equivalent resistance of the combination will be:
    • (a)nR (b) R/n   (c) n/R  (d) R/n2

    Ans-d

    1. The masses of three wires of copper are in the ratio of 1 : 3 : 5 and their lengths are in the ratio 5 : 3 : 1. The ratio of their electrical resistances is:
    • (a)1 : 3 : 5 (b) 5 : 3 : 1   (c) 1 : 15 : 125  (d) 125 : 15 : 1

    Ans-d

    1. Kirchhoff’s first law is based on the law of conservation of:
    • (a) charge     (b) energy   (c) momentum        (d) sum of mass and energy

    Ans-a

    1. Kirchhoff’s second law is based on the law of conservation of:
    • (a)charge    (b) energy          (c) momentum        (d) sum of mass and energy

    Ans-b

    1. A call of emf E is connected across a resistance r. The potential difference between the terminal of the cell is found to be V. The internal resistance of the cell must be:
    • (a) 2(E – V)V/r                                                                                       (b) 2(E – V)r/E                                                                                     (c) (E – V)r/V                                                                                        (d) (E – V)r

    Ans-c

       PDF of the Complete assignment of electric current is given below-

    To download the Complete assignment of electric current click here-

     

  • Complete assignment of electrostatics

    Complete assignment of electrostatics

    Complete assignment of electrostatics

    Students as you know , physics classes by Nayan jha already provided many kind of assignment of the chapter Electrostatics . But this is the Complete assignment of electrostatics . It contains objective type,fill in the blanks,1 marks,2 marks,3 marks and 5 marks questions with numerical and HOTS .

    Previously assignment of electrostatics , Objective questions of electrostatics , Important questions of electrostatics and numericals of electrostatics is already provided .In the previous assignment electric charges and field and electrostatics potential and capacitance are in different -different assignment . But here we are providing all kind of questions of both the chapters in one assignment .

    By clicking here students can see the complete syllabus of class 12th physics (CBSE) .

    It will help the students to revise complete chapter .which will help the students preparing for 12th board and all kind of competitive  examinations .

    Before to solve the questions of these assignment student must learn complete notes of these two chapters , electric charges and field and electrostatic potential and capacitance .

    To get the notes of  both the chapters of electrostatics click here-

    After revise the entire chapters of electric charges and field and electrostatic potential and electrostatics.Students may solve the questions of related chapters. Here is the Complete assignment of electrostatics  –

     To download the complete assignment Electric charges and field click here-

    To download the complete assignment Electrostatic potential and capacitors click here-

     

  • Energy stored in a capacitor and energy density

    Energy stored in a capacitor and energy density

    Energy stored in a capacitor and energy density .

    Before to know about the Energy stored in a capacitor and energy density , student must have to know about capacitors . To know about the capacitor click here–

    In this topic we will discuss about the Energy stored in a capacitor and energy density, when a capacitor is charged from zero to Q .

    ENERGY STORED IN A CAPACITOR –

    Suppose the plates of the capacitor is initially uncharged , and the charge is to be transferred from plate 2 to plate 1 , at a small time charge dQ transferred and at the final time it reaches from 0 to Q .   

     

    Let V is the potential difference across the plates then work done for small instant is

    dW = V . dQ  = (Q/C)dQ .

    integrating both sides,

    ∫ dW =∫(Q/C)dQ from limit 0 to Q ,  then we get ,

    net work done W = Q2/2C ,

    also as we know Q=CV,  so work done may be written as ,

    W = potential energy stored = U =( ½) CV2   = ½ QV .

    If we plot the graph  potential v/s charge we get,

     

    ***Similarly we can plot the graph (i)  U v/s V ( when C is constant )

    (ii) U v/s C (when V is constant)

    (iii) U v/s V  (when Q is constant)

    Total energy stored in the combination of capacitors –

    In  series combination –  U = Q2/2CS But in series combination 1/Cs = 1/C1  + 1/C2 + 1/C3   ….

    So we can write in series combination total energy U = U1 + U2 + U3 + …..

    In parallel combination – U = ½ Cp V2 = ½ C1 V2 + ½ C2 V2 + ½ C3V2 …..

    So we can write in parallel combination total energy of the combination   U = U1+ U2 + U3 ……

    Energy density of a  parallel plate capacitor –

    Energy density of the capacitor is the energy stored per unit volume of the capacitors or condensers . We can write energy density u = U/ ( volume )

    u = ( ½ C V2 )/ A d  ( Where A is the area of the plate and D is the separation between the plates .

    But potential V = E( electric field) d  . putting this value in the above equation we get  ,

    u = ½ ( ϵ0 A /d ) ( E2 d2 / Ad ) = ½ ϵ0 E2 .

    the  unit of energy density is  J/m3 .

     

     

  • Numerical based on electric charge ,electric field .

    Numerical based on electric charge ,electric field .

    Numerical based on electric charge ,electric field .

    Numerical based on electric dipole ( electric field at axial and equatorial point, torque and potential energy stored in dipole )-

    1. Two charges + 30μc and -30μc are placed 1cm apart . calculate electric field at a point on the the axial and equatorial line at a distance of 20 cm from the centre of the dipole .

    Ans- 6.25 x 105 N/C and 3,25 x 105‑ N/C .

    1. An electric dipole of dipole moment 4 x 10-5 C-m is placed in uniform electric field of 103 N/C making an angle of 300 with the direction of field . Determine the torque exerted by the electric field on the dipole.    Ans- 2 x 10-8Nm .
    2. An electric dipole is placed at an angle of 600 with an electric field of magnitude 4 x 105 N /C . It experience a torque of 8√3 Nm . If the length of the dipole is 2cm , determine the magnitude of either charge of the dipole . Ans –  2 x 10-3 C .
    3. An electric dipole of length 10cm having charges of magnitude 6 x 10-3 C , placed at 300 with respect to a uniform electric field experience a torque of magnitude 6√3 N-m . Calculate (i) magnitude of the field and (ii) potential energy of the dipole . Ans- 2√3x 104; -18J
    4. An electric dipole consist of two opposite charges of magnitude q=1×10-6C separated by 2.0 cm . The dipole is placed in an external electric field of 1×105 N/C . What maximum torque does the field exert on the dipole ? How much work must an external agent to do turn the dipole end for end , starting from position of alignment ( ϴ=00 ) . Ans- 2×10-3 N-m ; 4×10-3J .
    5. (i)Two point charges 4Q and Q are separated by 1m in air at what point on the line joining the two charges the electric field intensity is zero. (ii) Two identical metallic sphere A and B having charges +4Q and -10Q are kept at a certain distance apart . A third identical uncharged sphere C is first placed in contact with sphere A and then with sphere B . Spheres A and B are then brought in contact and then separated . Find the charges on the sphere A and B .

    7.Calculate the amount of work done in turning an electric dipole of dipole moment 3×108 C-m from its position of unstable equilibrium to stable equilibrium, in a uniform electric field of intensity 103N/c.

    8.The sum of two point charges is 7µc they repel each other with a force of 1N when kept 30 cm apart in free space , calculate the value of each charge.

    To download the complete assignment (pdf) based on numerical based on electric charge electric field click here-

     

  • Numerical based on electric field

    Numerical based on electric field

    Numerical based on electric field

    This topic contain numerical for the practice of the chapter electric field

    Before to solve the numerical based on electric field students has to study ( learn ) , and all the notes based on electric field , electric dipole ( axial and equatorial point)

    To read or download the notes on electric field click here-

    To read or download the notes on electric dipole , electric field at equatorial and axial point click here-

    Numerical based on electric field

    1. Two point charges +16μc and -9μc are placed 8cm apart in air . Determine the position of the point at which the resultant electric field is zero .          [ Ans-  24 cm]
    2. A particle of mass m and charge q is thrown at speed u against a uniform electric field E . How much distance will it travel before coming to momentary rest . ?   [Ans- mu2/2qE]
    3. A particle of mass m and charge q is released from rest in uniform electric field of intensity E . Calculate the kinetic energy it attains after moving a distance a distance x between the plates .   [Ans- qEx]
    4. Eight identical point charges of q coulomb each are placed at the corners of a cube of each side 0.1 m . calculate the electric field at the centre of the cube . calculate the field at the centre when one of the corner charge is removed .   [Ans – 0 ; 1.2 x 1012 .]
    5. Two charges + 30μc and -30μc are placed 1cm apart . calculate electric field at a point on the the axial and equatorial line at a distance of 20 cm from the centre of the dipole .                        [ Ans- 6.25 x 105 N/C and 3,25 x 105‑ N/C .]
    6. Four particles each of charge q are be placed on the vertices A ,B, C, D of a regular pentagon ABCDE . the distance of each corner from the centre is ‘a’ . Calculate the electric field at the centre of the pentagon .   [ Ans- q/4∏ϵ0 a2 along OE .]
    7. A small sphere of mass 1g carries a charge of +6μc . The sphere is suspended by a string in an electric field of 400N/C acting downwards. Calculate the tension in the string . What will be the tension if the charge on the sphere be -6μc .                                       [Ans- 1.22x 10-2 N . ; 74 x 10-4 N .]
    8. An electron falls through a distance of 1.5 cm in uniform electric field of value 2 x104N/C . when the direction of electric field is reversed , a proton falls through the same distance . compare the time of fall in each case .
    9. A particle of mass ‘m’ and charge -q enters the region between two charged plates initially moving along x-axis with speed vx ( as shown in the fig) . The length of the plate is L and an uniform electric field E is maintained between the plates . Show that the vertical deflection of the particle at the far edge of the plate is    QelL2 / (2m vx2) .                                                                                           
    10. As shown in the figure three charged particles in a uniform electrostatic field . Give the sign of three charges . Which particle has the highest charge to mass ratio .                                                             

     

  • Objective questions of ray optics

    Objective questions of ray optics

    Objective questions of ray optics

    this assignment will provide the important Objective questions of ray optics for  students preparing for class-12th board examination and for the students preparing for JEE/NEET and other competitive examinations.

    Reflection and Refraction of Light at Plane Surface ( Objective questions of ray optics)

    1. When light travels from glass to air, the incident angle is and the refraction angle is .the true relation is :(a)θ 1 =θ 2      (b)  θ 1 >θ2  (c)θ1 <θ2  (d)Not predictable
    2. Two mirrors are kept at 60 to each other and a body is placed in the middle.The total number of images formed is:(a)Three(b)Four (c)Five (d)Six
    3. If an object is placed unsymmetrically between two plane mirrors inclined at an angle 72 ,then the total number of images formed is:(a)5   (b)4    (c)2   (d)infinite
    4. If an object is placed symmetrically between two plane mirrors, inclined at an angle of 72 .than the total total number of images formed is:(a)5 (b)4 (c)2 (d)Infinite

    5) A ray of light is incident on a plane mirror at an angle of incidence of 30⁰ ,the deviation

    Produced by the mirror is :

    (a) 30 ⁰ ( b) 60⁰

    (c) 90⁰ (d) 120

    6) when a ray of light enters a glass slab from air:

    (a) its wavelength decreases

    (b) its wavelength decreases

    (c) its frequency increases

    (d) neither wavelength nor frequency changes

    7) When a light enters from air to water, then its:

    (a) frequency increases and speed decreases

    (b) frequency is the same but the wavelength is smaller in water then in air:

    (c) frequency is same but wavelength in water is greater than in air

    To download complete assignment of ray optics click here-objective ray optics

  • Objective questions of capacitance

    Objective questions of capacitance

    Objective questions of capacitance

    This assignment contains all important  objective questions of capacitance, it will be beneficial for the students preparing for class 12th board examination or preparing for JEE/NEET.

    Before to solve this assignment student must solve the assignment of its previous chapter electric field and potential, to download the assignment of objective questions of electric field and potential click here.

    Capacitance

    1. There are 27 drops of a conducting fluid. Each has a radius r and they are charged to a potential V0. These are combined to from a bigger drop. Its potential will be:
    • (a)V0      (b) 3V0    (c) 9V0          (d) 27V0
    1. 1000 small water drops each of radius r and charge q coalesce together to from one spherical drop. The potential of the bigger drop is larger than that of the smaller one by a factor:
    • (a)1000        (b) 100         (c) 10          (d) 1
    1. The capacitance of a parallel plate condenser does not depend upon:
    • (a)area of the plates
    • (b)medium between the plates
    • (c)distance between the plates
    • (d)metal of the plates
    1. The force between the plates of a parallel plate capacitor of capacitance C and distance of separation of the plates d with a potential difference V between the plates is:
    • (a)CV2/2d (b) C2V2/2d2    (c) C2V2/d2      (d) V2d/C
    1. A parallel plate capacitor is made by stacking n equally spaced plates connected alternately. If the capacitance between any two plates is C, then the resulting capacitance is:
    • (a)C    (b) nC         (c) (n-1)C        (d) (n+1)C
    1. Two parallel metal plates carry charge +Q and -Q respectively. A test charge q0 placed between them experiences a force F. Now the separation between the plates is doubled, then the force on the test charge will be:
    • (a)F         (b) 2F             (c) F/2              (d) F/4
    1. A 2μF capacitor is charged to a potential of 200 V and then isolated. When it is connected in parallel with a second capacitor which is uncharged, the common potential becomes 40 V. The capacitance of the second capacitor is:
    • (a)2μF        (b) 4μF        (c) 8μF       (d) none of these
    1. Three capacitors of capacitance 12μF each are available. The minimum and maximum capacitance which may be obtained from these are:
    • (a)12μF, 36μF (b) 4μF, 12μF    (c) 4μF, 36μF   (d) 0μF, ꚙμF

    To download entire assignment of objective questions of electric field click here -objective questions of Capacitance

     

    To solve the assignment of important objective  questions of electric current click here.

    electric- current
    electric- current

     

  • Objective questions of alternating current

    Objective questions of alternating current

    Objective questions of alternating current

    LC-OSCILLATOR

    This assignment (Objective questions of alternating current),provide the important objective questions of the chapter alternating current ,which is important for the students preparing for class-12th board examination or , other competitive examinations (JEE/NEET)

    Before to solve this assignment (Objective questions of alternating current), student should solve the assignment of objective questions of electromagnetic induction-

    1. A direct current of 5 amp is superimposed on an alternating current I = 10sin ɷt flowing through a wire. The effective value of the resulting current will be:
    • (a)(15/2) amp     (b) 5√3 amp  (c) 5√5 amp      (d) 15 amp
    1. In an AC circuit, a resistance of R ohm is connected in series with an inductance L. If phase angle between voltage and current is 45°, the value of inductive reactance will be:
    • (a)R/4
    • (b)R/2
    • (c)R
    • (d)cannot be found with the given data
    1. Resonance frequency of L – C circuit is:
    • (a)1/2π √LC       (b) 1/2πLC   (c) 1/2π √L/C   (d) 1/2π √LC
    1. In L-C-R series AC circuit, the phase angle between current and voltage is:
    • (a)any angle between 0 and ± π/2
    • (b)π/2
    • (c)π
    • (d)any angle between 0 and π
    1. In an L-C-R circuit, the capacitance is made one-fourth, when in resonance, so that the circuit remains in resonance?
    • (a)4 times    (b) (1/4) times       (c) 8 times        (d) 2 times

    TO download complete assignment of Objective questions of alternating Current- click here-