Physics Past Year Paper Compartment Anskey (Delhi Set -3) - 2014, Class 12, CBSE Class 12 Notes | EduRev

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Class 12 : Physics Past Year Paper Compartment Anskey (Delhi Set -3) - 2014, Class 12, CBSE Class 12 Notes | EduRev

 Page 1


 Compartment                                              Page No. 1                                               20
th
  July, 2014 Final 
MARKING SCHEME 
SET 55/1/3 (Compartment) 
Q.No. Expected Answer/Value Points 
 
Marks Total 
Marks 
1. Random motion of free electrons gets directed towards the point at a higher 
potential. 
Alternatively: 
Random motion becomes  a (partially) directed motion. 
1  
 
1 
2. Two monochromatic sources, which produce light waves, having a constant phase 
difference, are known as coherent sources. 
1 1 
3.  
 
 
 
 
     1 
 
 
 
 
 
 
 
 
1 
4. Paramagnetic material 1 1 
5. 
Effective power   
(Alternatively:  Effective power radiated decreases with an increase in 
wavelength.) 
 
1  
 
1 
6. Due to the heating effect of eddy currents set up in the metallic piece. 1 1 
7. When a constant current flows through a wire, the Potential difference, between 
any two points on the wire of uniform cross section, is directly proportional to the 
length of the wire between these points. 
Alternatively: 
V  or   = constant 
1  
 
 
 
1 
8. i. The two point charges(  and ) should be of opposite nature. 
ii. Magnitude of charge  must be greater than that of charge  
½ 
½ 
 
1 
9  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
½  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Drawing of magnetic field lines   ½  
Obtaining the expression for magnetic field  1 ½  
Page 2


 Compartment                                              Page No. 1                                               20
th
  July, 2014 Final 
MARKING SCHEME 
SET 55/1/3 (Compartment) 
Q.No. Expected Answer/Value Points 
 
Marks Total 
Marks 
1. Random motion of free electrons gets directed towards the point at a higher 
potential. 
Alternatively: 
Random motion becomes  a (partially) directed motion. 
1  
 
1 
2. Two monochromatic sources, which produce light waves, having a constant phase 
difference, are known as coherent sources. 
1 1 
3.  
 
 
 
 
     1 
 
 
 
 
 
 
 
 
1 
4. Paramagnetic material 1 1 
5. 
Effective power   
(Alternatively:  Effective power radiated decreases with an increase in 
wavelength.) 
 
1  
 
1 
6. Due to the heating effect of eddy currents set up in the metallic piece. 1 1 
7. When a constant current flows through a wire, the Potential difference, between 
any two points on the wire of uniform cross section, is directly proportional to the 
length of the wire between these points. 
Alternatively: 
V  or   = constant 
1  
 
 
 
1 
8. i. The two point charges(  and ) should be of opposite nature. 
ii. Magnitude of charge  must be greater than that of charge  
½ 
½ 
 
1 
9  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
½  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Drawing of magnetic field lines   ½  
Obtaining the expression for magnetic field  1 ½  
 Compartment                                              Page No. 2                                               20
th
  July, 2014 Final 
Alternatively: 
  
 
 
Applying Ampere circuital law for the rectangular loop abcd 
  =  
Bh = (nh) 
B =  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
½  
 
 
 
½  
 
½  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
2 
10.  
 
 
(i) Intensity of incident radiation I = nhv,  
where n is number of photons incident per unit time per unit area. 
For same intensity of two monochromatic radiations of frequency             
 and  
 =  
As  >  
?  
Therefore the number of electrons emitted for monochromatic radiation of 
frequency , will be more than that for radiation of frequency  
[Alternatively: Also accept if the student says that, for same intensity of incident 
radiation, the number of emitted electrons is same for each of the two frequencies 
of incident radiation.] 
(i) hv =  
For given  (work function of metal) 
increases with  
  Maximum Kinetic energy of emitted photoelectrons will be more for 
monochromatic light of frequency as  > ) 
 
 
 
 
 
½  
 
 
 
 
 
½  
 
 
 
 
½  
 
 
½  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
2 
Explanation of parts (i) and (ii)    1+1 
Page 3


 Compartment                                              Page No. 1                                               20
th
  July, 2014 Final 
MARKING SCHEME 
SET 55/1/3 (Compartment) 
Q.No. Expected Answer/Value Points 
 
Marks Total 
Marks 
1. Random motion of free electrons gets directed towards the point at a higher 
potential. 
Alternatively: 
Random motion becomes  a (partially) directed motion. 
1  
 
1 
2. Two monochromatic sources, which produce light waves, having a constant phase 
difference, are known as coherent sources. 
1 1 
3.  
 
 
 
 
     1 
 
 
 
 
 
 
 
 
1 
4. Paramagnetic material 1 1 
5. 
Effective power   
(Alternatively:  Effective power radiated decreases with an increase in 
wavelength.) 
 
1  
 
1 
6. Due to the heating effect of eddy currents set up in the metallic piece. 1 1 
7. When a constant current flows through a wire, the Potential difference, between 
any two points on the wire of uniform cross section, is directly proportional to the 
length of the wire between these points. 
Alternatively: 
V  or   = constant 
1  
 
 
 
1 
8. i. The two point charges(  and ) should be of opposite nature. 
ii. Magnitude of charge  must be greater than that of charge  
½ 
½ 
 
1 
9  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
½  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Drawing of magnetic field lines   ½  
Obtaining the expression for magnetic field  1 ½  
 Compartment                                              Page No. 2                                               20
th
  July, 2014 Final 
Alternatively: 
  
 
 
Applying Ampere circuital law for the rectangular loop abcd 
  =  
Bh = (nh) 
B =  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
½  
 
 
 
½  
 
½  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
2 
10.  
 
 
(i) Intensity of incident radiation I = nhv,  
where n is number of photons incident per unit time per unit area. 
For same intensity of two monochromatic radiations of frequency             
 and  
 =  
As  >  
?  
Therefore the number of electrons emitted for monochromatic radiation of 
frequency , will be more than that for radiation of frequency  
[Alternatively: Also accept if the student says that, for same intensity of incident 
radiation, the number of emitted electrons is same for each of the two frequencies 
of incident radiation.] 
(i) hv =  
For given  (work function of metal) 
increases with  
  Maximum Kinetic energy of emitted photoelectrons will be more for 
monochromatic light of frequency as  > ) 
 
 
 
 
 
½  
 
 
 
 
 
½  
 
 
 
 
½  
 
 
½  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
2 
Explanation of parts (i) and (ii)    1+1 
 Compartment                                              Page No. 3                                               20
th
  July, 2014 Final 
11. 
 
 
 
 
 
Total magnification 
    =  
 
 
 
 
 
 
 
 
 
1 
 
 
 
 
 
 
 
1 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
2 
12. 
 
 
 
 
 
 
 
 
Work done in bringing the charge  from infinity to position 
Hence, total work done in assembling the  two charges 
OR 
 
 
 
 
 
Work done in moving a unit  positive charge along distance  
 =  
             = V – (V + 
             = - 
           E= -  
(i) Electric field is in the direction in which the potential decreases steepest. 
(ii) Magnitude of Electric field is given by the change in the magnitude of 
potential per unit displacement, normal to the equipotential surface at the 
point. 
 
 
 
 
½  
 
 
½ +½  
 
 
 
½  
 
 
 
 
 
 
 
½  
 
 
½  
 
½  
 
½  
 
 
 
 
 
 
 
 
 
 
 
2 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
2 
 
 
 
Ray diagram of formation of image by a compound microscope 1 
Expression for total magnification     1 
Obtaining the expression for total work done   2 
Derivation  of relation between Electric field and potential gradient  1 
Two important conclusions      ½ + ½   
Page 4


 Compartment                                              Page No. 1                                               20
th
  July, 2014 Final 
MARKING SCHEME 
SET 55/1/3 (Compartment) 
Q.No. Expected Answer/Value Points 
 
Marks Total 
Marks 
1. Random motion of free electrons gets directed towards the point at a higher 
potential. 
Alternatively: 
Random motion becomes  a (partially) directed motion. 
1  
 
1 
2. Two monochromatic sources, which produce light waves, having a constant phase 
difference, are known as coherent sources. 
1 1 
3.  
 
 
 
 
     1 
 
 
 
 
 
 
 
 
1 
4. Paramagnetic material 1 1 
5. 
Effective power   
(Alternatively:  Effective power radiated decreases with an increase in 
wavelength.) 
 
1  
 
1 
6. Due to the heating effect of eddy currents set up in the metallic piece. 1 1 
7. When a constant current flows through a wire, the Potential difference, between 
any two points on the wire of uniform cross section, is directly proportional to the 
length of the wire between these points. 
Alternatively: 
V  or   = constant 
1  
 
 
 
1 
8. i. The two point charges(  and ) should be of opposite nature. 
ii. Magnitude of charge  must be greater than that of charge  
½ 
½ 
 
1 
9  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
½  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Drawing of magnetic field lines   ½  
Obtaining the expression for magnetic field  1 ½  
 Compartment                                              Page No. 2                                               20
th
  July, 2014 Final 
Alternatively: 
  
 
 
Applying Ampere circuital law for the rectangular loop abcd 
  =  
Bh = (nh) 
B =  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
½  
 
 
 
½  
 
½  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
2 
10.  
 
 
(i) Intensity of incident radiation I = nhv,  
where n is number of photons incident per unit time per unit area. 
For same intensity of two monochromatic radiations of frequency             
 and  
 =  
As  >  
?  
Therefore the number of electrons emitted for monochromatic radiation of 
frequency , will be more than that for radiation of frequency  
[Alternatively: Also accept if the student says that, for same intensity of incident 
radiation, the number of emitted electrons is same for each of the two frequencies 
of incident radiation.] 
(i) hv =  
For given  (work function of metal) 
increases with  
  Maximum Kinetic energy of emitted photoelectrons will be more for 
monochromatic light of frequency as  > ) 
 
 
 
 
 
½  
 
 
 
 
 
½  
 
 
 
 
½  
 
 
½  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
2 
Explanation of parts (i) and (ii)    1+1 
 Compartment                                              Page No. 3                                               20
th
  July, 2014 Final 
11. 
 
 
 
 
 
Total magnification 
    =  
 
 
 
 
 
 
 
 
 
1 
 
 
 
 
 
 
 
1 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
2 
12. 
 
 
 
 
 
 
 
 
Work done in bringing the charge  from infinity to position 
Hence, total work done in assembling the  two charges 
OR 
 
 
 
 
 
Work done in moving a unit  positive charge along distance  
 =  
             = V – (V + 
             = - 
           E= -  
(i) Electric field is in the direction in which the potential decreases steepest. 
(ii) Magnitude of Electric field is given by the change in the magnitude of 
potential per unit displacement, normal to the equipotential surface at the 
point. 
 
 
 
 
½  
 
 
½ +½  
 
 
 
½  
 
 
 
 
 
 
 
½  
 
 
½  
 
½  
 
½  
 
 
 
 
 
 
 
 
 
 
 
2 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
2 
 
 
 
Ray diagram of formation of image by a compound microscope 1 
Expression for total magnification     1 
Obtaining the expression for total work done   2 
Derivation  of relation between Electric field and potential gradient  1 
Two important conclusions      ½ + ½   
 Compartment                                              Page No. 4                                               20
th
  July, 2014 Final 
13.  
 
 
 
P:              NOT Gate 
Q:             AND Gate 
Input A Output Y 
0 1 
1 0 
NOT gate 
 
 
 
 
½  
½  
 
½  
 
½  
 
 
 
 
 
 
 
 
 
2 
14.  
 
 
Equivalent magnetic moment of the coil  
 =IA 
 =I b 
( = unit vector  to the plane of the coil) 
Torque =  
  =  I b 
               = 0 
(as  are parallel or antiparallel, to each other) 
[Note: Also give credit, when student obtains the relation  
, and substitutes  and writes  
 
 
 
 
 
½  
 
 
½  
½  
½ 
 
 
 
 
 
 
 
 
 
 
 
 
 
2 
15.  
 
 
 =  
As  = 0  
?  =  
?  =  =  
?  
 wavelength ( )of emitted electrons,   
 
 
 
 
½ 
 
 
 
½  
 
½  
 
 
 
 
 
 
 
 
½  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
2 
Naming of gates P and Q     ½  + ½  
Truth Table of combination &  Identification  ½  + ½  
Obtaining the expression for the torque  2  
Finding the relation      1 ½  
Drawing the graph      ½  
Page 5


 Compartment                                              Page No. 1                                               20
th
  July, 2014 Final 
MARKING SCHEME 
SET 55/1/3 (Compartment) 
Q.No. Expected Answer/Value Points 
 
Marks Total 
Marks 
1. Random motion of free electrons gets directed towards the point at a higher 
potential. 
Alternatively: 
Random motion becomes  a (partially) directed motion. 
1  
 
1 
2. Two monochromatic sources, which produce light waves, having a constant phase 
difference, are known as coherent sources. 
1 1 
3.  
 
 
 
 
     1 
 
 
 
 
 
 
 
 
1 
4. Paramagnetic material 1 1 
5. 
Effective power   
(Alternatively:  Effective power radiated decreases with an increase in 
wavelength.) 
 
1  
 
1 
6. Due to the heating effect of eddy currents set up in the metallic piece. 1 1 
7. When a constant current flows through a wire, the Potential difference, between 
any two points on the wire of uniform cross section, is directly proportional to the 
length of the wire between these points. 
Alternatively: 
V  or   = constant 
1  
 
 
 
1 
8. i. The two point charges(  and ) should be of opposite nature. 
ii. Magnitude of charge  must be greater than that of charge  
½ 
½ 
 
1 
9  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
½  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Drawing of magnetic field lines   ½  
Obtaining the expression for magnetic field  1 ½  
 Compartment                                              Page No. 2                                               20
th
  July, 2014 Final 
Alternatively: 
  
 
 
Applying Ampere circuital law for the rectangular loop abcd 
  =  
Bh = (nh) 
B =  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
½  
 
 
 
½  
 
½  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
2 
10.  
 
 
(i) Intensity of incident radiation I = nhv,  
where n is number of photons incident per unit time per unit area. 
For same intensity of two monochromatic radiations of frequency             
 and  
 =  
As  >  
?  
Therefore the number of electrons emitted for monochromatic radiation of 
frequency , will be more than that for radiation of frequency  
[Alternatively: Also accept if the student says that, for same intensity of incident 
radiation, the number of emitted electrons is same for each of the two frequencies 
of incident radiation.] 
(i) hv =  
For given  (work function of metal) 
increases with  
  Maximum Kinetic energy of emitted photoelectrons will be more for 
monochromatic light of frequency as  > ) 
 
 
 
 
 
½  
 
 
 
 
 
½  
 
 
 
 
½  
 
 
½  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
2 
Explanation of parts (i) and (ii)    1+1 
 Compartment                                              Page No. 3                                               20
th
  July, 2014 Final 
11. 
 
 
 
 
 
Total magnification 
    =  
 
 
 
 
 
 
 
 
 
1 
 
 
 
 
 
 
 
1 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
2 
12. 
 
 
 
 
 
 
 
 
Work done in bringing the charge  from infinity to position 
Hence, total work done in assembling the  two charges 
OR 
 
 
 
 
 
Work done in moving a unit  positive charge along distance  
 =  
             = V – (V + 
             = - 
           E= -  
(i) Electric field is in the direction in which the potential decreases steepest. 
(ii) Magnitude of Electric field is given by the change in the magnitude of 
potential per unit displacement, normal to the equipotential surface at the 
point. 
 
 
 
 
½  
 
 
½ +½  
 
 
 
½  
 
 
 
 
 
 
 
½  
 
 
½  
 
½  
 
½  
 
 
 
 
 
 
 
 
 
 
 
2 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
2 
 
 
 
Ray diagram of formation of image by a compound microscope 1 
Expression for total magnification     1 
Obtaining the expression for total work done   2 
Derivation  of relation between Electric field and potential gradient  1 
Two important conclusions      ½ + ½   
 Compartment                                              Page No. 4                                               20
th
  July, 2014 Final 
13.  
 
 
 
P:              NOT Gate 
Q:             AND Gate 
Input A Output Y 
0 1 
1 0 
NOT gate 
 
 
 
 
½  
½  
 
½  
 
½  
 
 
 
 
 
 
 
 
 
2 
14.  
 
 
Equivalent magnetic moment of the coil  
 =IA 
 =I b 
( = unit vector  to the plane of the coil) 
Torque =  
  =  I b 
               = 0 
(as  are parallel or antiparallel, to each other) 
[Note: Also give credit, when student obtains the relation  
, and substitutes  and writes  
 
 
 
 
 
½  
 
 
½  
½  
½ 
 
 
 
 
 
 
 
 
 
 
 
 
 
2 
15.  
 
 
 =  
As  = 0  
?  =  
?  =  =  
?  
 wavelength ( )of emitted electrons,   
 
 
 
 
½ 
 
 
 
½  
 
½  
 
 
 
 
 
 
 
 
½  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
2 
Naming of gates P and Q     ½  + ½  
Truth Table of combination &  Identification  ½  + ½  
Obtaining the expression for the torque  2  
Finding the relation      1 ½  
Drawing the graph      ½  
 Compartment                                              Page No. 5                                               20
th
  July, 2014 Final 
16.  
 
 
 
 
i. emf induced 
e =   
   = 0.25 x 15 x 10
-2
 x 25 
   = 0.9375 volt 
   = 0.94 volt 
ii. Current in the loop  
 i =  
   =    = 0.23 A 
 
 
 
 
 
 
½  
 
½  
 
 
½  
 
½  
 
 
 
 
 
 
 
 
 
 
 
 
 
2 
17.  
 
 
 
(ii) Conductor                                            (ii)  Semiconductor 
 
                      
   =  
In conductors, average relaxation time decreases with increase in temperature, 
resulting in an increase in resistivity. 
In semiconductors,  the increase in number density (with increase in temperature) 
is more than the decrease in relaxation time; the net result is, therefore, a  decrease 
in resistivity. 
 
 
 
 
 
 
 
 
½ + ½  
 
 
 
 
 
 
 
 
 ½  
 
 
½  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
2 
18.  
 
 
Charge on inner surface  :  - Q 
Charge on outer surface  :  + Q 
 
Electric field at point  
                               E   = 
 
 
 
½ 
½  
 
 
1 
 
 
 
 
 
 
 
 
2 
19.  
 
 
(i) In diffraction pattern, intensity will be minimum at an angle  
 There will be a first minimum at an angle  on either side of   
             central maximum 
 
 
 
½ 
 
 
 
 
 
 
 
 
Calculation of  
i.  emf induced in the arm PQ    1 
ii. Current induced in the loop    1 
Drawing the two plots      ½ + ½  
Explanation of Behaviour     ½ + ½  
Charges on the inner and outer surfaces  ½ + ½  
Expression for electric field    1 
Explanation of part (i) and (ii)     1 ½ + 1 ½  
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