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Do you want 100% Marks with less
effort Prepare the Following YSA Paper for YOU.?
Class – XII
Subject - Physics
( Based on the new
pattern of CBSE board examination )
ELECTROSTATICS
( NCERT units 1 and 2 )
Time Allowed : 3 hours Maximum Marks :
70
(a) All questions are compulsory
(b) Question numbers 1 to 8 are very
short answer type questions, carrying one mark each.
(c) Question numbers 9 to 18 are short
answer type questions, carrying two marks each.
(d) Question numbers 19 to 27 carry
three marks each.
(e) Question numbers 28 to 30 are long
answer type questions, carrying five marks each.
(f) Use of calculators is not permitted.
However, you may use log tables, if necessary.
Q.1> How many protons will have the
total charge of 1C
Q.2> What is the dielectric constant
of Silver?
Q.3> Find the electric field b/w 2
metal plates 5mm apart, connected by a 12V battery.
Q.4> Write the value of Coulomb
constant ( K ) and mention its units.
Q.5> Find the work done in placing a
charge of 8nC on a condenser of capacity 100micro-farad.
Q.6> Define equipotential surface and
draw EPS for a single point charge.
Q.7> What is the angle b/w electric
dipole moment and the electric field on its equatorial
point?
Q.8> Sketch electric field lines for
a dipole.
Q.9> The electrostatic force on a
small sphere of charge 4C due to another small sphere of
charge 8C in air is F. What is the distance b/w the 2
spheres. What is the force on the –8C sphere due to the
first sphere. What will the force be if the spheres are
dipped in a liquid having dielectric constant K
Q.10> An electron is placed inside a
capacitor ( 5μf ). It is found to be stationary i.e.
its weight is
balanced by the electrostatic force.
Find the potential difference across the plates of the
capacitor if the plate area is A.
Q.11> Equal charges each of 1C are
placed at x = 0, 2 , 4 , 8 , 16 cm. Find the force
experienced by the charge at x=2 cm. Define electric field
intensity at x=2 and find it.
Q.12> What is the work done in moving
a charge 100nC from point A to point B 5cms apart, where
both points A and B lie on the same equipotential surface?
Explain your answer.
Q.13> Define electric flux. Is it a
vector quantity. Give its units. If the flux entering and
leaving a closed surface is Φ1 and Φ2 find the
charge inside that surface.
Q.14> Define electric potential. What
is line integral of electric field over a closed loop?
Q.15> Can a positively charged object
attract a neutral object? Explain briefly
Q.16> A
uniform electric field E exists b/w the 2 charged plates as
shown in the
figure. What would be the
work done in moving a charge q along the path A B
ABCDA. Hence define
conservative fields and give 2 properties.
Q.17> Write 2 differences b/w charge
and mass.
Q.18> Calculate the potential at the
center of a square of side 1.414m, which
carries at its 4 corner charges of 2nC ,
1nC , -2nC , -3nC respectively.
Q.19> Two point charges 4q and q are
fixed a distance 2m apart. Find the point on the line
joining them at which the net electric field intensity in
zero. What is the potential at this point. If a charge of
magnitude –3q is placed at this point, in which direction
will it move. What will be its potential energy at this
point?
Q.20> Charges of 4μC
each are placed at the four corners of a
square of side 1m. Find the
electric field and potential at the center. Q1
What would these quantities be if one of
the given charges were negative? 4m
Q.21> Three charges –Q1 , +Q2 , -Q3
are placed as shown in the 3m
figure. Find in vector form
the force acting on Q2 charge. Q2 -Q3
Q.22> When 2
capacitors C1 and C2 are connected in series the net is 1.2
farad, when connected in parallel the net capacitance is 5
farad. Find C1 and C2.
Q.23>
Find the equivalent capacitance b/w points A and B.
Each
capacitor is of 1μfarad
Q.24> A hollow sphere of radius R is
given a charge Q. On a graph plot the variation of Electric
field intensity versus distance from center. On another
graph plot the potential against distance.
Q.25> Two point electric charges A
and B of unknown magnitude and sign are placed d distance
apart. The electric field is zero at a point, not b/w the
charges but on the line joining them and closer to A. Write
2 essential conditions for this to happen
Q.26> Explain dielectric
polarization. A certain region of space is to be protected
from external electric field. Suggest a suitable method.
Q.27> What are electric field lines?
Give 4 properties and define neutral point.
Q.28> Define capacitance and give its
units. Explain the principle of a parallel plate capacitor
and the use of earthing. Derive the formula for capacitance
of a parallel plate capacitor with a slab.
Q.29> State Gauss’s theorem. Give
its mathematical expression. Derive an expression for the
electric field intensity at any point due to an infinite
plane sheet of charge of density σ C/m2
Q.30> Using a proper figure, explain
the construction and working of a VanDeGraff generator.
OR
Q.30>( choice 2 ) Use Gauss’s law
to obtain an expression for the electric field due to an
infinitely long straight uniformly charged wire.
(b) Electric field in the given figure
is directed along + X direction and given by
Ex = 5Ax + 2B, where E is in NC-1 and A
= 10 and B = 5 in SI units. x is in metre.
calculate.
(i) the electric flux through the cube.
ii) net charge enclosed within the
cube.
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