Download 2013_CBSE_XIIScience_4_1_SET3_sectionA

Class XII_Delhi_Physics_Set-3
General Instructions:
(i) All questions are compulsory.
(ii) There are 29 questions in total. Question Nos. 1 to 8 are very short answer type questions
and carry one mark each.
(iii) Questions Nos. 9 to 16 carry two marks each. Questions Nos. 17 to 25 carry three marks
each and questions Nos. 27 to 29 carry five marks each.
(iv) There is no overall choice. However, an internal choice has been provided in one question of
two marks, one question of three marks and all three questions of five marks each. You have to
attempt only one of the choices in such questions.
(v) Questions No. 26 is value based question carries four marks.
(vi) Use of calculators is not permitted. However, you may use log tables if necessary.
(vii) You may use the following value of physical constants wherever necessary:
c = 3 × 108 m/s
h = 6.63 × 10–34 Js
e = 1.6 × 10–9 C
0 = 4π × 10–7 T m A–1
1
 9 109 N m 2 C2
4με 0
me = 9.1 × 10–31 kg
Mass of the Neutron = 1.675 × 10–27 kg
Mass of the Proton = 1.673 × 10–27 kg
1.
What is the geometrical shape of equipotential surfaces due to a single isolated charge?
Ans.
For an isolated charge the equipotential surfaces are co-centric spherical shells and the
distance between the shells increases with the decrease in electric field.
Class XII_Delhi_Physics_Set-3
2.
Write the relationship between angle of incidence ‘i’, angle of prism ‘A’ and angle of
minimum deviations for a triangular prism.
Ans.
The relation between the angle of incidence I, angle of prism, A and the angle of
A  m
minimum deviation, ∆m for a triangular prism is given as is given by i 
.
2
3.
A capacitor has been charged by a dc source. What are the magnitude of conduction and
displacement current, when it is fully charged?
Ans.
q
.
o
Here, q  constant, the capacitor is fully charged.
Electric flux through plates of capacitor, φ E 
q
d 

d E
Displacement current , ID  o
 o  o   0
dt
dt
dV
Conduction current, I  C
 0 as voltage becomes constant
dt
when the capacitor becomes fully charged.
Transverse waves can oscillate in the direction perpendicular to the direction of its
propagation but longitudinal waves like sound waves oscillate only along the direction of
its propagation. So, longitudinal waves cannot be polarized.
4.
The given graph shows the variation of photo-electric current (I) versus applied voltage
(V) for two difference photosensitive materials and for two different intensities of the
incident radiations. Identify the pairs of curves that correspond to different materials but
same intensity of incident radiation.
Ans.
Curves 1 and 2 correspond to similar materials while curves 3 and 4 represent different
materials, since the value of stopping potential for the pair of curves (1 and 2) & (3 and
4) are the same. For given frequency of the incident radiation the stopping potential is
independent of its intensity.
Class XII_Delhi_Physics_Set-3
So, the pairs of curves (1 and 3) and (2 and 4) correspond to different materials but same
intensity of incident radiation.
5.
Which of the following waves can be polarized (i) Heat waves (ii) Sound waves? Give
reason to support your answer.
Ans.
Heat waves can be polarized because heat waves are transverse waves whereas sound
waves cannot be polarized because sound waves are longitudinal waves.
6.
A 5 V battery of negligible internal resistance is connected across a 200 V battery and a
resistance of 39 as shown in the figure. Find the value of the current in circuit.
Ans.
Let I be the current flowing in the circuit.
Using Kirchoff’s law,
39I=200-5
195
I=
5 A
39
7.
Which of the following substances are para-magnetic?
Bi, Al, Cu, Ca, Pb, Ni
Ans.
Paramagnetic substances are Aluminum (Al) and Calcium (Ca).
8.
A heating element is marked 210 V, 630 W. Find the resistance of the element when
connected to a 210 V dc source.
Ans.
V2
V 2 2102
 Power is given as, P 
, R 

 70 
R
P
630