Electrostatics- 1 Practice Questions - DPP for NEET

 Page 1


DIRECTIONS (Q.1-Q.18) : There are 18 multiple choice
questions. Each question has 4 choices (a), (b), (c) and (d), out
of which ONLY ONE choice is correct.
Q.1 A total charge Q is broken in two parts 
1
Q and 
2
Q and they
are placed at a distance R from each other. The maximum
force of repulsion between them will occur, when
(a)
21
Q,
QQ
QQ
RR
= =- (b)21
2
Q,
43
QQ
QQ = =-
(c)
21
3
Q,
44
QQ
Q == (d)
12
Q,
22
==
QQ
Q
Q.2 Two small balls each having the charge + Q are suspended
by insulating threads of length L from a hook. This
arrangement is taken in space where there is no
gravitational effect, then the angle between the two
suspensions and the tension in each thread will be
(c)
2
2
0
1
180,
4
2
pÎ
Q
L
o
(d)
2
2
0
1
180,
4pÎ
Q
L
o
Q.3 Electric charges of 1 ,1 CC m -m and 2 C m are placed in air at
the corners A,B and C respectively of an equilateral triangle
ABC having length of each side 10 cm. The resultant force
on the charge at C is
(a) 0.9 N (b) 1.8N (c) 2.7 N (d) 3.6 N
Q.4 An electron is moving round the nucleus of a hydrogen
atom in a circular orbit of radius . r The coulomb force
F
ur
between the two is (here 
0
1
)
4
=
pÎ
K
(a)
2
3
e
Kr
r
-
$
(b)
2
3
e
Kr
r
r
(c)
2
3
e
Kr
r
-
r
(d)
2
2
e
Kr
r
$
Page 2


DIRECTIONS (Q.1-Q.18) : There are 18 multiple choice
questions. Each question has 4 choices (a), (b), (c) and (d), out
of which ONLY ONE choice is correct.
Q.1 A total charge Q is broken in two parts 
1
Q and 
2
Q and they
are placed at a distance R from each other. The maximum
force of repulsion between them will occur, when
(a)
21
Q,
QQ
QQ
RR
= =- (b)21
2
Q,
43
QQ
QQ = =-
(c)
21
3
Q,
44
QQ
Q == (d)
12
Q,
22
==
QQ
Q
Q.2 Two small balls each having the charge + Q are suspended
by insulating threads of length L from a hook. This
arrangement is taken in space where there is no
gravitational effect, then the angle between the two
suspensions and the tension in each thread will be
(c)
2
2
0
1
180,
4
2
pÎ
Q
L
o
(d)
2
2
0
1
180,
4pÎ
Q
L
o
Q.3 Electric charges of 1 ,1 CC m -m and 2 C m are placed in air at
the corners A,B and C respectively of an equilateral triangle
ABC having length of each side 10 cm. The resultant force
on the charge at C is
(a) 0.9 N (b) 1.8N (c) 2.7 N (d) 3.6 N
Q.4 An electron is moving round the nucleus of a hydrogen
atom in a circular orbit of radius . r The coulomb force
F
ur
between the two is (here 
0
1
)
4
=
pÎ
K
(a)
2
3
e
Kr
r
-
$
(b)
2
3
e
Kr
r
r
(c)
2
3
e
Kr
r
-
r
(d)
2
2
e
Kr
r
$
DPP/ P 32
at B will be
(a)
2
2
0
3
4pÎ
q
a
(b)
2
2
0
q
a pÎ
(c)
2
2
0
1 22
2
4
æö
+
ç÷
èø pÎ
q
a
(d)
2
2
0
1
2
2 4
æö
+
ç÷
èø
pÎ
q
a
Q 6 . Electric lines of force about negative point charge are
(a) Circular, anticlockwise (b) Circular, clockwise
(c) Radial, inward (d) Radial, outward
Q 7 . The magnitude of electric field intensity 
E
is such that,
an electron placed in it would experience an electrical
force equal to its weight is given by
(a) mge (b)
mg
e
(c)
e
mg
(d)
2
2
e
g
m
Q 8 . Two point charges Q and –3Q are placed at some distance apart.
If the electric field at the location of Q is E then at the locality
of –3Q, it is
(a) –E (b) E/3 (c) –3E (d) –E/3
Q 9 . Charges , 2 ,3 q q q and 4q are placed at the corners A, B, C
and D of a square as shown in the following figure. The
direction of electric field at the centre of the square is
parallel to side.
(a) AB
(b) CB
(c) BD
A B
D C
O
4q 3q
2q
q
(d) AC
Q. 0 1 Three infinitely long non-conducting charge sheets are
placed as shown in figure. The electric field at point P is
(a)
$
0
2
k
s
e
 (b) – 
$
0
2
k
s
e
(c)
$
0
4
k
s
e
P
Z
x
Za = – 
Za = 
Za = 3
2 -s
(d) – 
$
0
4
k
s
e
Q. 1 1 The electric intensity due to an infinite cylinder of radius
R and having charge q per unit length at a distance r(r > R)
from its axis is
(a) Directly proprotional to r
2
 (b) Directly proprotional to r
3
(c) Inversely proprotional to r
(d) Inversely proprotional to r
2
Q. 2 1 A sphere of radius R has a uniform distribution of electric
charge in its volume. At a distance x from its centre, for
x < R, the eletric field is directly proportional to
(a)
2
1
x
(b)
1
x
(c) x (d) x
2
Q. 3 1 A  charged ball B hangs from a silk thread S, which makes an
angle q with a large charged conducting sheet P, as shown
Page 3


DIRECTIONS (Q.1-Q.18) : There are 18 multiple choice
questions. Each question has 4 choices (a), (b), (c) and (d), out
of which ONLY ONE choice is correct.
Q.1 A total charge Q is broken in two parts 
1
Q and 
2
Q and they
are placed at a distance R from each other. The maximum
force of repulsion between them will occur, when
(a)
21
Q,
QQ
QQ
RR
= =- (b)21
2
Q,
43
QQ
QQ = =-
(c)
21
3
Q,
44
QQ
Q == (d)
12
Q,
22
==
QQ
Q
Q.2 Two small balls each having the charge + Q are suspended
by insulating threads of length L from a hook. This
arrangement is taken in space where there is no
gravitational effect, then the angle between the two
suspensions and the tension in each thread will be
(c)
2
2
0
1
180,
4
2
pÎ
Q
L
o
(d)
2
2
0
1
180,
4pÎ
Q
L
o
Q.3 Electric charges of 1 ,1 CC m -m and 2 C m are placed in air at
the corners A,B and C respectively of an equilateral triangle
ABC having length of each side 10 cm. The resultant force
on the charge at C is
(a) 0.9 N (b) 1.8N (c) 2.7 N (d) 3.6 N
Q.4 An electron is moving round the nucleus of a hydrogen
atom in a circular orbit of radius . r The coulomb force
F
ur
between the two is (here 
0
1
)
4
=
pÎ
K
(a)
2
3
e
Kr
r
-
$
(b)
2
3
e
Kr
r
r
(c)
2
3
e
Kr
r
-
r
(d)
2
2
e
Kr
r
$
DPP/ P 32
at B will be
(a)
2
2
0
3
4pÎ
q
a
(b)
2
2
0
q
a pÎ
(c)
2
2
0
1 22
2
4
æö
+
ç÷
èø pÎ
q
a
(d)
2
2
0
1
2
2 4
æö
+
ç÷
èø
pÎ
q
a
Q 6 . Electric lines of force about negative point charge are
(a) Circular, anticlockwise (b) Circular, clockwise
(c) Radial, inward (d) Radial, outward
Q 7 . The magnitude of electric field intensity 
E
is such that,
an electron placed in it would experience an electrical
force equal to its weight is given by
(a) mge (b)
mg
e
(c)
e
mg
(d)
2
2
e
g
m
Q 8 . Two point charges Q and –3Q are placed at some distance apart.
If the electric field at the location of Q is E then at the locality
of –3Q, it is
(a) –E (b) E/3 (c) –3E (d) –E/3
Q 9 . Charges , 2 ,3 q q q and 4q are placed at the corners A, B, C
and D of a square as shown in the following figure. The
direction of electric field at the centre of the square is
parallel to side.
(a) AB
(b) CB
(c) BD
A B
D C
O
4q 3q
2q
q
(d) AC
Q. 0 1 Three infinitely long non-conducting charge sheets are
placed as shown in figure. The electric field at point P is
(a)
$
0
2
k
s
e
 (b) – 
$
0
2
k
s
e
(c)
$
0
4
k
s
e
P
Z
x
Za = – 
Za = 
Za = 3
2 -s
(d) – 
$
0
4
k
s
e
Q. 1 1 The electric intensity due to an infinite cylinder of radius
R and having charge q per unit length at a distance r(r > R)
from its axis is
(a) Directly proprotional to r
2
 (b) Directly proprotional to r
3
(c) Inversely proprotional to r
(d) Inversely proprotional to r
2
Q. 2 1 A sphere of radius R has a uniform distribution of electric
charge in its volume. At a distance x from its centre, for
x < R, the eletric field is directly proportional to
(a)
2
1
x
(b)
1
x
(c) x (d) x
2
Q. 3 1 A  charged ball B hangs from a silk thread S, which makes an
angle q with a large charged conducting sheet P, as shown
DPP/ P 32
in the figure. The surface charge density s of the sheet is
proportional to
(a) sin q
+
+
+
+
+
+
+
q
S
B
P
(b) tan q
(c) cos q
(d) cot q
Q. 4 1 A charge q is placed at the centre of a cube. Then the flux
passing through one face of cube will be
(a)
0
Î
q
(b)
0
2 Î
q
(c)
0
4 Î
q
(d)
0
6 Î
q
DIRECTIONS (Q. 5 1 ) : In the following question,
more than one of the answers  given are correct. Select
the correct answers and mark it according to the following
codes:
Codes :
(a) 1, 2 and 3 are correct (b) 1 and 2 are correct
(c) 2 and 4 are correct (d) 1 and 3 are correct
Q. 5 1 A solid sphere S
1
 is connected to a charge reservoir through
a heater H as shown in figure.
Solid
sphere
Solid
sphere
H
Heater
S
1
S
2
Flux through a closed spherical surface around S
1
 is given
by f = a t
2
 where a is a constant and t is time in seconds.
If resistance of heater is R then select correct statements
(1) Power consumed by heater will be 4a
2
e
0
2
 Rt
2
.
(2) Electric flux through a closed spherical surface around
S
2
 will be – a t
2
.
(3) Rate of change of electric flux through a closed
spherical surface around S
2
 will be –2a t
(4) All of the above are correct
DIRECTIONS (Q. 6 1 -Q. 8 1 ) : Read the passage given below
and answer the questions that follows :
A sphere of radius R contains charge density ( ) ( ), r ARr r =-
for 
0. rR <<
 The total electric charge inside the sphere is Q.
Q. 6 1 The value of A in terms of Q and R is
(a)
2
4
2Q
R p
(b)
4
3Q
R p
(c)
2
3
3Q
R p
(d) 
3Q
R p
Q. 7 1 The electric field inside the sphere is
(a) 
2
2
0
3 11
34
Q rr
RR
R
éù
æö æö
ê -ú
ç÷ ç÷
èø èø êú Î
ëû
(b) 
2 2
3
12 11
34
Q rr
RR
R
éù
æ ö æö
ê -ú
ç ÷ ç÷
è ø èø êú
ëû
(c) 
2
2
0
120 11
43
5
éù
æö æö
ê -ú
ç÷ ç÷
èø èø êú Î
ëû
Q rr
RR
R
(d) 
2
2
1211
34
rr
RR
RQ
éù
æö æö
- êú
ç÷ ç÷
èø èø
êú
ëû
Q. 8 1 The electric field outside the sphere is 
0
1
4
k
æö
=
ç÷
pÎ
èø
(a)
kQ
r
(b)
2
kQ
r
(c)
3
kQ
r
(d)
2
2
kQ
r
DIRECTIONS (Q. 9 1 -Q. 0 2 ) : Each of these questions
contains two statements: Statement-1 (Assertion) and
Statement-2 (Reason). Each of these questions has four
alternative choices, only one of which is the correct answer.
You have to select the correct choice.
(a) Statement-1 is True, Statement-2 is True; Statement-2 is a
correct explanation for  Statement-1.
(b) Statement-1 is True, Statement-2 is True; Statement-2 is
NOT a correct explanation for Statement-1.
(c) Statement -1 is False, Statement-2 is True.
(d) Statement -1 is True, Statement-2 is False.
Q. 9 1 Statement-1 : Electric lines of force cross each other.
Statement-2 : Electric field at a point superimpose to give
Page 4


DIRECTIONS (Q.1-Q.18) : There are 18 multiple choice
questions. Each question has 4 choices (a), (b), (c) and (d), out
of which ONLY ONE choice is correct.
Q.1 A total charge Q is broken in two parts 
1
Q and 
2
Q and they
are placed at a distance R from each other. The maximum
force of repulsion between them will occur, when
(a)
21
Q,
QQ
QQ
RR
= =- (b)21
2
Q,
43
QQ
QQ = =-
(c)
21
3
Q,
44
QQ
Q == (d)
12
Q,
22
==
QQ
Q
Q.2 Two small balls each having the charge + Q are suspended
by insulating threads of length L from a hook. This
arrangement is taken in space where there is no
gravitational effect, then the angle between the two
suspensions and the tension in each thread will be
(c)
2
2
0
1
180,
4
2
pÎ
Q
L
o
(d)
2
2
0
1
180,
4pÎ
Q
L
o
Q.3 Electric charges of 1 ,1 CC m -m and 2 C m are placed in air at
the corners A,B and C respectively of an equilateral triangle
ABC having length of each side 10 cm. The resultant force
on the charge at C is
(a) 0.9 N (b) 1.8N (c) 2.7 N (d) 3.6 N
Q.4 An electron is moving round the nucleus of a hydrogen
atom in a circular orbit of radius . r The coulomb force
F
ur
between the two is (here 
0
1
)
4
=
pÎ
K
(a)
2
3
e
Kr
r
-
$
(b)
2
3
e
Kr
r
r
(c)
2
3
e
Kr
r
-
r
(d)
2
2
e
Kr
r
$
DPP/ P 32
at B will be
(a)
2
2
0
3
4pÎ
q
a
(b)
2
2
0
q
a pÎ
(c)
2
2
0
1 22
2
4
æö
+
ç÷
èø pÎ
q
a
(d)
2
2
0
1
2
2 4
æö
+
ç÷
èø
pÎ
q
a
Q 6 . Electric lines of force about negative point charge are
(a) Circular, anticlockwise (b) Circular, clockwise
(c) Radial, inward (d) Radial, outward
Q 7 . The magnitude of electric field intensity 
E
is such that,
an electron placed in it would experience an electrical
force equal to its weight is given by
(a) mge (b)
mg
e
(c)
e
mg
(d)
2
2
e
g
m
Q 8 . Two point charges Q and –3Q are placed at some distance apart.
If the electric field at the location of Q is E then at the locality
of –3Q, it is
(a) –E (b) E/3 (c) –3E (d) –E/3
Q 9 . Charges , 2 ,3 q q q and 4q are placed at the corners A, B, C
and D of a square as shown in the following figure. The
direction of electric field at the centre of the square is
parallel to side.
(a) AB
(b) CB
(c) BD
A B
D C
O
4q 3q
2q
q
(d) AC
Q. 0 1 Three infinitely long non-conducting charge sheets are
placed as shown in figure. The electric field at point P is
(a)
$
0
2
k
s
e
 (b) – 
$
0
2
k
s
e
(c)
$
0
4
k
s
e
P
Z
x
Za = – 
Za = 
Za = 3
2 -s
(d) – 
$
0
4
k
s
e
Q. 1 1 The electric intensity due to an infinite cylinder of radius
R and having charge q per unit length at a distance r(r > R)
from its axis is
(a) Directly proprotional to r
2
 (b) Directly proprotional to r
3
(c) Inversely proprotional to r
(d) Inversely proprotional to r
2
Q. 2 1 A sphere of radius R has a uniform distribution of electric
charge in its volume. At a distance x from its centre, for
x < R, the eletric field is directly proportional to
(a)
2
1
x
(b)
1
x
(c) x (d) x
2
Q. 3 1 A  charged ball B hangs from a silk thread S, which makes an
angle q with a large charged conducting sheet P, as shown
DPP/ P 32
in the figure. The surface charge density s of the sheet is
proportional to
(a) sin q
+
+
+
+
+
+
+
q
S
B
P
(b) tan q
(c) cos q
(d) cot q
Q. 4 1 A charge q is placed at the centre of a cube. Then the flux
passing through one face of cube will be
(a)
0
Î
q
(b)
0
2 Î
q
(c)
0
4 Î
q
(d)
0
6 Î
q
DIRECTIONS (Q. 5 1 ) : In the following question,
more than one of the answers  given are correct. Select
the correct answers and mark it according to the following
codes:
Codes :
(a) 1, 2 and 3 are correct (b) 1 and 2 are correct
(c) 2 and 4 are correct (d) 1 and 3 are correct
Q. 5 1 A solid sphere S
1
 is connected to a charge reservoir through
a heater H as shown in figure.
Solid
sphere
Solid
sphere
H
Heater
S
1
S
2
Flux through a closed spherical surface around S
1
 is given
by f = a t
2
 where a is a constant and t is time in seconds.
If resistance of heater is R then select correct statements
(1) Power consumed by heater will be 4a
2
e
0
2
 Rt
2
.
(2) Electric flux through a closed spherical surface around
S
2
 will be – a t
2
.
(3) Rate of change of electric flux through a closed
spherical surface around S
2
 will be –2a t
(4) All of the above are correct
DIRECTIONS (Q. 6 1 -Q. 8 1 ) : Read the passage given below
and answer the questions that follows :
A sphere of radius R contains charge density ( ) ( ), r ARr r =-
for 
0. rR <<
 The total electric charge inside the sphere is Q.
Q. 6 1 The value of A in terms of Q and R is
(a)
2
4
2Q
R p
(b)
4
3Q
R p
(c)
2
3
3Q
R p
(d) 
3Q
R p
Q. 7 1 The electric field inside the sphere is
(a) 
2
2
0
3 11
34
Q rr
RR
R
éù
æö æö
ê -ú
ç÷ ç÷
èø èø êú Î
ëû
(b) 
2 2
3
12 11
34
Q rr
RR
R
éù
æ ö æö
ê -ú
ç ÷ ç÷
è ø èø êú
ëû
(c) 
2
2
0
120 11
43
5
éù
æö æö
ê -ú
ç÷ ç÷
èø èø êú Î
ëû
Q rr
RR
R
(d) 
2
2
1211
34
rr
RR
RQ
éù
æö æö
- êú
ç÷ ç÷
èø èø
êú
ëû
Q. 8 1 The electric field outside the sphere is 
0
1
4
k
æö
=
ç÷
pÎ
èø
(a)
kQ
r
(b)
2
kQ
r
(c)
3
kQ
r
(d)
2
2
kQ
r
DIRECTIONS (Q. 9 1 -Q. 0 2 ) : Each of these questions
contains two statements: Statement-1 (Assertion) and
Statement-2 (Reason). Each of these questions has four
alternative choices, only one of which is the correct answer.
You have to select the correct choice.
(a) Statement-1 is True, Statement-2 is True; Statement-2 is a
correct explanation for  Statement-1.
(b) Statement-1 is True, Statement-2 is True; Statement-2 is
NOT a correct explanation for Statement-1.
(c) Statement -1 is False, Statement-2 is True.
(d) Statement -1 is True, Statement-2 is False.
Q. 9 1 Statement-1 : Electric lines of force cross each other.
Statement-2 : Electric field at a point superimpose to give
4
DPP/ P 32
one resultant electric field.
Q. 0 2 Statement-1 : A point charge is brought in an electric field. The
field at a nearby point will increase, whatever be the nature of
the charge.
Statement-2 : The electric field is dependent on the nature of
charge.