MAALEE EDUCATION PVT LTD
YLP – PHYSICS TEST – ELECTROSTATICS (02.12.2017)
1.
2.
3.
Two positive point charge of 12 µC and 8 µC are
10 cm apart. The work done in bringing them
4 cm closer is,
(1) 1.3 eV
(2) 13 J
(3) 5.8 J
(4) 5.8 Ev
The electric field, at a distance of 20 cm from the
centre of a dielectric sphere of radius 10 cm is,100
V/m. Then E at 3 cm distance from the centre of
sphere is:
(1) 100 V/m
(2) 125 V/m
(3) 120 V/m
(4) zero
5.
6.
8.
An electric dipole is placed at an angle of 30° with
5
an electric field intensity 2 × 10 N/C. It
experiences a torque equal to 4 N m. The charge
on the dipole, if the dipole length is 2 cm, is
(A) 8 Mc
(B) 2 mC
(C) 5 mC
(D) 7 µC
A combination of capacitors is set up as shown in
the figure. The magnitude of the electric field, due
to a point charge Q (having a charge equal to the
sum of the charges on the 4 µF and 9 µF
capacitors), at a point distant 30 m from it, would
equal :
A charge q is placed in the middle of a line joining
the two equal and like point charges Q. This system
will remain in equilibrium for which the value of q is
!
4.
7.
!
(1) –
(2) –
(3)
(4) –
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An elementary particle of mass m and charge +e is
projected with velocity v at a much more massive
particle of charge Ze, where Z > 0. What is the
closest possible approach of the incident particle.
(a)
(b)
(c)
(d)
Two point charges + 9e and +e are kept 16 cm
apart to each other. Where should a third charge q
be placed between them so that the system
remains in the equilibrium state :
(1) 24 cm from + 9e
(2) 12 cm from + 9e
(3) 24 cm from + e
(4) 12 cm from + e
A square surface of side L meter in the plane of the
paper is placed in a uniform electric field E (volt/m)
acting along the same plane at an angle θ with the
horizontal side of the square as shown in figure.
The electric flux linked to the surface, in units of
volt–m, is :-
(1) Zero
2
(3) EL cosθ
2
(2) EL
2
(4) EL sinθ
9.
(A) 360 N/C
(B) 420 N/C
(C) 480 N/C
(D) 240 N/C
A, B and C are three points in a uniform electric
field. The electric potential is
(A) Maximum at A
(B) Maximum at B
(C) Maximum at C
(D) Same at all the three points A, B and C
10. Three concentric metallic spherical shells of radii R,
2R, 3R, are given charges Q1, Q2, Q3,
respectively. It is found that the surface charge
densities on the outer surfaces of the shells are
equal. Then, the ratio of the charges given to the
shells, Q1 : Q2 : Q3, is
(A) 1 : 2 : 3
(B) 1 : 3 : 5
(C) 1 : 4 : 9
(D) 1 : 8 : 18
11. Two identical charged spheres are suspended by
strings of equal lengths. The strings make an angle
of 30° with each other. When suspended in a liquid
–3
of density 0.8 g cm , the angle remains the same.
–3
If density of the material of the sphere is 1.6 gcm ,
the dielectric constant of the liquid is
(A) 1
(B) 4
(C) 3
(D) 2
12. A capacitor of 2 µF is charged as shown in the
diagram. When the switch S is turned to position 2,
the percentage of its stored energy dissipated is
17. The rate of alpha partical falls on neutral spheare is
12
10 per second. The time in whichsphere gets
charged by 2µc is ......... sec.
(A) 2.25 (B) 3.15
(C) 6.25
(D) 1.66
18. Two equal negative charges –q are fixed at points
(0, a) and (0, –a). A positive charge Q isreleased
from rest at the point (2a, o) on the X - axis. The
charge Q will ..........
(A) 75%
(B) 80%
(A) move to the origin and remain at rest there
(C) 0%
(D) 20%
(B) execute simple harmonic motion about the
origin
13. A parallel plate air capacitor of capacitance C is
connected to a cell of emf V and then disconnected
from it. A dielectric slab of dielectric constant K,
which can just fill the air gap of the capacitor, is now
inserted in it. Which of the following is incorrect?
(A) The potential difference between the plates
decreases K times
(C) move to infinity
(D) execute oscillations but not simple harmonic
motion
19. For the system shown in figure, if the resultant
force on q is zero, then Q = ...............
(B) The energy stored in the capacitor decreases K
times
(C) The change in energy stored is
(D) The charge on the capacitor is not conserved
14. Two charges, each equal to q, are kept at x = – a
and x = a on the x-axis. A particle of mass m and
charge q0 = q/2 is placed at the origin. If charge q0
is given a small displacement (y << a) along the
y-axis, the net force acting on the particle is
proportional to
(A) y
(B) –y
(C)
(D)
15. Two spherical conductors A and B of radii 1 mm
and 2 mm are separated by a distance of 5 cm and
are uniformly charged. If the spheres are connected
by a conducting wire then in equilibrium condition,
the ratio of the magnitude of the electric fields at the
surface of spheres A and B is
(A) 1 : 4
(B) 4 : 1
(C) 1 : 2
(D) 2 : 1
16. Consider a neutral conducting sphere. A positive
point charge is placed outside the sphere. The net
charge on the sphere is then,
(A) negative and distributed uniformly over the
surface of the sphere
(B) negative and appears only at the point on the
sphere closest to the point charge
(C) negative and distributed non-uniformly over the
entire surface of the sphere
(D) zero
(A) –2√2 Q
(B) 2 √2 Q
(C) 2 √3Q
(D) –3 √2 Q
20. Two equal negative charges –q are fixed at points
(o, a) and (o, –a) on the Y axis. A positive charge q
is released from rest at the point x (x << a) on the
X-axis, then the frequency of motion is .........
(A)
(B)
(C)
(D)
21. An inclined plane making an angle of 30o with the
horizontal is placed in an uniform electric field
E = 100 Vm–1. A particle of mass 1 kg and charge
0.01 c is allowed to slide down from rest from a
height of 1m. If the coefficient of friction is 0.2 the
time taken by the particle to reach the bottom is
.......... sec.
(A) 2.337 (B) 4.337
(C) 5
(D) 1.337
22. Two point masses m each carrying charge –q and
+q are attached to the ends of a massless rigid
non-conducting rod of length l. The arrangement is
placed in a uniform electric field E such that the
rod makes a small angle 5o with the field direction.
The minimum time needed by the rod to align
itself along the field is ........
(A)
(B)
(C)
(D)
23. Three charges 2q, –q, –q are located at the vertices
of an equilateral triangle. At the centre of the
triangle.
(A) The Field is Zero but Potential is non - zero
(B) The Field is non - Zero but Potential is zero
(C) Both field and Potential are Zero
(D) Both field and Potential are non- Zero
24. Two charged spheres of radii R1 and R2 having
equal surface charge density. The ratio of their
potential is ...
(A)
)* $
)*
(B) ,
)+
)+ $
(C) ,
)*
-
(D)
)+
-
)+
)*
25. Two positive point charges of 12μc and 8μc are
10 cm apart each other. The work done in bringing
them 4cm closer is .....
(A) 5.8 J (B) 13 eV
(C) 5.8 eV (D) 13 J
26. A ball of mass 1 gm and charge 10–8 c moves from
a point A, where the potential is 600 volt
to the point B where the potential is zero. Velocity
of the ball of the point B is 20cm/s. The velocity of
the ball at the point A will be .....
.
(A) 16.8
(C) 228
/
0.
/
(B) 22.8
0.
/
.
(D) 168
(C)
(D)
28. Two parallel plate air capacitors have their plate
areas 100 and 500 cm2 respectively. If they have
the same charge and potential and the distance
between the plates of the first capacitor is 9.5 mm,
what is the distance between the plates of the
second capacitor?
(A) 0.25 cm (B) 0.50 cm
(C) 0.75 cm (D) 1 cm
29. A parallel plate air capacitor has a capacitance
18μF. If the distance between the plates is tripled
and a dielectric medium is introduced, the
capacitance becomes 72μF. The dielectric constant
of the medium is
(A) 4 (B) 12
(C) 9
(D) 2
30. There are 10 condensers each of capacity 5μF. The
ratio between maximum and minimum capacities
obtained from these condensers will be
(A) 40 : 1 (B) 25 : 5
(C) 60 : 3 (D) 100 : 1
31. In the arrangement of capacitors shown in figure,
each capacitor is of 9μF, then the equivalent
capacitance between the points A and B is
(A) 18μF
(B) 9μF
(C) 15μF
(D) 4.5μF
32. A thin spherical shell of radius R has change Q
spread uniformly over its surface. Which of the
following graphs, figure most closely represents
the electric field E (r) produced by the shell in the
range 0 ≤ r <∞ , where r is the distance from the
centre of the shell.
/
27. Two thin wire rings each having a radius R are
placed at a distance d apart with their axes
coinciding. The charges on the two rings are +q and
–q. The potential difference between the centres
of the two rings is ....
(A)
(B)
(C)
(D)
(A) 0 (B)
33. For circuit the equivalent capacitance between
points P and Q is
(A) 6 C
"
(C) C
$
(B) 4 C
(D)
2
33
(A) 41.80
(C) 40.80
C
34. Two metal plate form a parallel plate capacitor.
The distance between the plates is d. A metal
sheet of thickness d/2 and of the same area is I
ntroduced between the plates. What is the ratio of
the capacitance in the two cases ?
(A) 4 : 1 (B) 3 : 1
(C) 2 : 1
(D) 5 : 1
35. A parallel plate air capacitor has a capacitance C.
When it is half filled with a dielectric of dielectric
constant 5, the percentage increase in the
capacitance will be
(A) 200 % (B) 33.3 % (C) 400 %
(D) 66.6 %
36. An electric circuit requires a total capacitance of
2μF across a potential of 1000 V. Large number of
1μF capacitances are available each of which
would breakdown if the potential is more then
350 V. How many capacitances are required to
make the circuit ?
(A) 24 (B) 12
(C) 20
(D) 18
37. Two point charges repel each other with a force of
100 N. One of the charges is increased by 10% and
other is reduced by 10%. The new force of
repulsion at the same distance would be ........ N.
(A) 121 (B) 100
(C) 99
(D) 89
38. A copper sphere of mass 2 gm contains about
2 × 1022 atoms. The charge on the nucleus ofeach
atom is 29e. The fraction of electrons removed.
(A) 2 ×10–10
(B) 1.19 × 10–12
(C) 1.25 ×10–11
(D) 2.16 × 10–11
39. Two point charges of +16μc and –9μc are placed
8 cm apart in air. ............... distance of a point from
–9μc charge at which the resultant electric field is
zero.
(A) 24 cm
(B) 9 cm
(C) 16 cm
(D) 35 cm
of a silk fibre 5 cm long. The other end of the fibre
is attached to a large vertical conducting plate
which has a surface charge of 25×10–6Cm–2 , on
each side. When system is freely hanging the angle
fibre makes with vertical is ...............
40. A small sphere whose mass is 0.1 gm carries a
charge of 3×10–10C and is tieup to one end
(B) 450
(D) 45.80
41. Two uniformaly charged spherical conductors A
and B having radius 1mm and 2mm are separated
by a distance of 5 cm. If the spheres are connected
by a conducting wire then in equilibrium condition,
the ratio of the magnitude of the electric fields at
the surfaces of spheres A and B is .........
(A) 4 : 1
(C) 2 : 1
(B) 1 : 2
(D) 1 : 4
42. In Millikan’s oil drop experiment an oil drop
carrying a charge Q is held stationary by a p.d.
2400v between the plates. To keep a drop of half
the radius stationary the potential difference had
to be made 600 v. What is the charge on the
second drop ?
(A)
"!
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(C) Q
(B)
(D)
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43. A charged particle of mass 1 kg and charge 2μc is
thrown from a horizontal ground at an angle
θ = 45o with speed 20m/s. In space a horizontal
electric field E = 2 ×107V/m exist. The range on
horizontal ground of the projectile thrown is
(A) 100 m
(B) 50 m
(C) 200 m
(D) 0 m
44. At what angle θ a point P must be located from
dipole axis so that the electric field intensity at the
point is perpendicular to the dipole axis ?
(A) 53° to 54°
(B) 50° to 51°
(C) 45° to 46°
(D) 52° to 53°
45. An oil drop of 12 excess electrons is held stationary
under a constant electric field of 2.55×104Vm–1 .
If the density of the oil is 1.26 gm/cm3 then the
radius of the drop is .......... m.
(A) 9.81×10–7
(B) 9.29×10–7
(C) 9.38×10–8
(D) 9.34×10–8