Magnetic Effects of Current- 1 Practice Questions - DPP for NEET

 Page 1


DIRECTIONS (Q.1-Q.19) : There are 19 multiple choice
questions. Each question has 4 choices (a), (b), (c) and (d), out
of which ONLY ONE choice is correct.
Q.1 The magnitude of magnetic field at a point having
perpendicular distance 50 mm from a long straight
conducting wire carrying a current of 3A is
(a) 0.12 G (b) 1.2 G
(c) 12 G (d) 0.012 G
Q.2 A circular arc of wire of radius of curvature r subtends an
angle of  p/4 radian at its centre. If  i  current is  flowing in
it then the magnetic induction at its centre is -
(a)
0
i
8r
m
(b)
0
i
4r
m
(c)
0
i
16r
m
(d)0
Q.3 A current i is flowing in a conductor PQRST shaped as
shown in the figure. The radius of curved part QRS is r and
length of straight portions PQ and ST is very large. The
magnetic field at the centre O of the curved part  is -
90°
O
Q
R
r
i
P
T
x
y
z
i
S
(a)
0
µi 3
ˆ
1k
4r2
p éù
+
êú
p
ëû
(b)
0
µi 3
ˆ
1k
4r2
p éù
-
êú
pëû
(c)
0
µi 3
ˆ
1 ( k)
4r2
p éù
+-
êú
p
ëû
(d)
0
µi3
ˆ
1 ( k)
4r2
p éù
--
êú
pëû
Page 2


DIRECTIONS (Q.1-Q.19) : There are 19 multiple choice
questions. Each question has 4 choices (a), (b), (c) and (d), out
of which ONLY ONE choice is correct.
Q.1 The magnitude of magnetic field at a point having
perpendicular distance 50 mm from a long straight
conducting wire carrying a current of 3A is
(a) 0.12 G (b) 1.2 G
(c) 12 G (d) 0.012 G
Q.2 A circular arc of wire of radius of curvature r subtends an
angle of  p/4 radian at its centre. If  i  current is  flowing in
it then the magnetic induction at its centre is -
(a)
0
i
8r
m
(b)
0
i
4r
m
(c)
0
i
16r
m
(d)0
Q.3 A current i is flowing in a conductor PQRST shaped as
shown in the figure. The radius of curved part QRS is r and
length of straight portions PQ and ST is very large. The
magnetic field at the centre O of the curved part  is -
90°
O
Q
R
r
i
P
T
x
y
z
i
S
(a)
0
µi 3
ˆ
1k
4r2
p éù
+
êú
p
ëû
(b)
0
µi 3
ˆ
1k
4r2
p éù
-
êú
pëû
(c)
0
µi 3
ˆ
1 ( k)
4r2
p éù
+-
êú
p
ëû
(d)
0
µi3
ˆ
1 ( k)
4r2
p éù
--
êú
pëû
2
DPP/ P 39
Q.4 Consider the loop PQRSP , carrying clockwise current i, shown
in the figure. The magnitude of magnetic field at the centre O of
the curved portion is
(a)
0
i
2r
m
p
 [p – f + tan f]
(b)
0
i
2r
m
p
R Q P
i i
S
O
r
f f
(
(c)0
(d)
0
i
2r
m
p
 [p – f + tan f]
Q.5 A circular coil of 0.2 m diameter has 100 turns and carries a
current of 0.1 ampere. The intensity of magnetic field at the
centre of the coil is -
(a) 6.28 × 10
–4
 N/A.m (b) 62.8 × 10
–4
 N/A.m
(c) 6.28 × 10
–5
 N/A.m (d) 62.8 × 10
–5
 N/A.m
Q.6 For the arrangement of two current carrying identical coils
shown in the figure, the magnetic field at the center O is
(N a nd a re pre se nt nu m be r o f turns and rad iu s of e a c h c oil)-
Coil-2
Coil-1
I
I
x
y
z
(a)
0
NI
2a
m
(b)
0
NI
2 2a
m
(c)
0
NI
2
m
(d)
0
NI
2a
m
Q.7 A current is flowing through a conducting hollow pipe
whose area of cross-section is shown in the fig. The value
of magnetic induction will be zero at-
(a) Point P, Q and R
• Q

R
P • (b) Point R but not at P and Q
(c) Point Q but not at P and R
(d) Point P but not at Q and R
Q.8 Dimensional formula of m
0
 is-
(a) MLT
–2 
A
–2
(b) MLT
–2
A
–2
(c) MLT
–2
 A
2
(d) MLT
2
 A
2
Q.9 A current of 1.0 ampere is flowing in the sides of an equilateral
triangle of side 4.5 × 10
–2
 m. Find the magnetic field at the
centroid of the triangle.
(Permeability constant m
0
 = 4p × 10
–7
 V-s/A-m).
(a) 4.0 × 10
–5
 weber/m
2
(b) 6.0 × 10
–8
 weber/m
2
(c) 2.0 × 10
–5
 weber/m
2
(d) 7.0 × 10
–12
 weber/m
2
Q.10 An air-solenoid has 500 turns of wire in its 40 cm length.
If the current in the wire be 1.0 ampere then the magnetic
field on the axis inside the solenoid is -
(a) 15.7 gauss (b) 1.57 gauss
(c) 0.157 gauss (d) 0.0157 gauss
Q.11 A solenoid of length 0.2m has 500 turns on it. If
8.71 × 10
–6
 Weber/m
2
 be the magnetic field at an end of
the solenoid, then the current flowing in the solenoid is –
(a)
0.174
p
A (b) 
0.0174
p
A (c)
17.4
p
A (d)
174
p
A
Q.12 A circular current carrying coil has a radius R. The distance
from the centre of the coil on the axis where the magnetic
induction will be 
1
8
th
 to its value at the centre of the coil,
is
(a)
R
3
(b) R3 (c)
2 3R
(d)
2
R
3
Q.13 The average radius of an air cored made toroid is 0.1 m
and it has 500 turns. If it carries 0.5 ampere current, then
the magnetic field inside it is :
(a) 5 × 10
–4
 tesla (b) 5 × 10
–3
 tesla
(c) 5 × 10
–2
 tesla (d) 2 × 10
–3
 tesla
Q.14The straight long conductors AOB and COD are
perpendicular to each other and carry current i
1
 and i
2
. The
magnitude of the magnetic induction at point P at a distance
a from the point O in a direction perpendicular to the plane
ACBD is
(a) ( )
0
12
µ
2pa
ii +
(b) ( )
0
12
µ
2pa
ii -
A
B
C D
i
1
i
2
B
1
B
2
P
O
a
(c) ( )
1/2
22 0
12
µ
2pa
ii +
(d)
( )
0 12
12
µ
2pa
ii
ii +
Page 3


DIRECTIONS (Q.1-Q.19) : There are 19 multiple choice
questions. Each question has 4 choices (a), (b), (c) and (d), out
of which ONLY ONE choice is correct.
Q.1 The magnitude of magnetic field at a point having
perpendicular distance 50 mm from a long straight
conducting wire carrying a current of 3A is
(a) 0.12 G (b) 1.2 G
(c) 12 G (d) 0.012 G
Q.2 A circular arc of wire of radius of curvature r subtends an
angle of  p/4 radian at its centre. If  i  current is  flowing in
it then the magnetic induction at its centre is -
(a)
0
i
8r
m
(b)
0
i
4r
m
(c)
0
i
16r
m
(d)0
Q.3 A current i is flowing in a conductor PQRST shaped as
shown in the figure. The radius of curved part QRS is r and
length of straight portions PQ and ST is very large. The
magnetic field at the centre O of the curved part  is -
90°
O
Q
R
r
i
P
T
x
y
z
i
S
(a)
0
µi 3
ˆ
1k
4r2
p éù
+
êú
p
ëû
(b)
0
µi 3
ˆ
1k
4r2
p éù
-
êú
pëû
(c)
0
µi 3
ˆ
1 ( k)
4r2
p éù
+-
êú
p
ëû
(d)
0
µi3
ˆ
1 ( k)
4r2
p éù
--
êú
pëû
2
DPP/ P 39
Q.4 Consider the loop PQRSP , carrying clockwise current i, shown
in the figure. The magnitude of magnetic field at the centre O of
the curved portion is
(a)
0
i
2r
m
p
 [p – f + tan f]
(b)
0
i
2r
m
p
R Q P
i i
S
O
r
f f
(
(c)0
(d)
0
i
2r
m
p
 [p – f + tan f]
Q.5 A circular coil of 0.2 m diameter has 100 turns and carries a
current of 0.1 ampere. The intensity of magnetic field at the
centre of the coil is -
(a) 6.28 × 10
–4
 N/A.m (b) 62.8 × 10
–4
 N/A.m
(c) 6.28 × 10
–5
 N/A.m (d) 62.8 × 10
–5
 N/A.m
Q.6 For the arrangement of two current carrying identical coils
shown in the figure, the magnetic field at the center O is
(N a nd a re pre se nt nu m be r o f turns and rad iu s of e a c h c oil)-
Coil-2
Coil-1
I
I
x
y
z
(a)
0
NI
2a
m
(b)
0
NI
2 2a
m
(c)
0
NI
2
m
(d)
0
NI
2a
m
Q.7 A current is flowing through a conducting hollow pipe
whose area of cross-section is shown in the fig. The value
of magnetic induction will be zero at-
(a) Point P, Q and R
• Q

R
P • (b) Point R but not at P and Q
(c) Point Q but not at P and R
(d) Point P but not at Q and R
Q.8 Dimensional formula of m
0
 is-
(a) MLT
–2 
A
–2
(b) MLT
–2
A
–2
(c) MLT
–2
 A
2
(d) MLT
2
 A
2
Q.9 A current of 1.0 ampere is flowing in the sides of an equilateral
triangle of side 4.5 × 10
–2
 m. Find the magnetic field at the
centroid of the triangle.
(Permeability constant m
0
 = 4p × 10
–7
 V-s/A-m).
(a) 4.0 × 10
–5
 weber/m
2
(b) 6.0 × 10
–8
 weber/m
2
(c) 2.0 × 10
–5
 weber/m
2
(d) 7.0 × 10
–12
 weber/m
2
Q.10 An air-solenoid has 500 turns of wire in its 40 cm length.
If the current in the wire be 1.0 ampere then the magnetic
field on the axis inside the solenoid is -
(a) 15.7 gauss (b) 1.57 gauss
(c) 0.157 gauss (d) 0.0157 gauss
Q.11 A solenoid of length 0.2m has 500 turns on it. If
8.71 × 10
–6
 Weber/m
2
 be the magnetic field at an end of
the solenoid, then the current flowing in the solenoid is –
(a)
0.174
p
A (b) 
0.0174
p
A (c)
17.4
p
A (d)
174
p
A
Q.12 A circular current carrying coil has a radius R. The distance
from the centre of the coil on the axis where the magnetic
induction will be 
1
8
th
 to its value at the centre of the coil,
is
(a)
R
3
(b) R3 (c)
2 3R
(d)
2
R
3
Q.13 The average radius of an air cored made toroid is 0.1 m
and it has 500 turns. If it carries 0.5 ampere current, then
the magnetic field inside it is :
(a) 5 × 10
–4
 tesla (b) 5 × 10
–3
 tesla
(c) 5 × 10
–2
 tesla (d) 2 × 10
–3
 tesla
Q.14The straight long conductors AOB and COD are
perpendicular to each other and carry current i
1
 and i
2
. The
magnitude of the magnetic induction at point P at a distance
a from the point O in a direction perpendicular to the plane
ACBD is
(a) ( )
0
12
µ
2pa
ii +
(b) ( )
0
12
µ
2pa
ii -
A
B
C D
i
1
i
2
B
1
B
2
P
O
a
(c) ( )
1/2
22 0
12
µ
2pa
ii +
(d)
( )
0 12
12
µ
2pa
ii
ii +
DPP/ P 39
3
Q.15 A conducting circular loop of radius r carries a constant
current i. It is placed in a uniform magnetic field B
ur
, such
that B
ur
 is perpendicular to the plane of the loop. The
magnetic force acting on the loop is
(a) ir B
ur
(b)2pri B
ur
(c) zero (d) pri B
ur
Q.16 The radius of a circular loop is r and a current i is flowing
in it. The equivalent magnetic moment will be
(a) ir (b) 2pir (c) ipr
2
(d)
2
1
r
Q.17 A current of 30 A is flowing in a vertical straight wire. If
the horizontal component of earth's magnetic field is 2 ×
10
–5
 tesla then the distance of null point from wire is -
(a) 0.9 m (b) 0.3 mm (c) 0.3 cm (d) 0.3 m
Q.18 A charged particle is released from rest in a region of steady
uniform electric and magnetic fields which are parallel to
each other. The particle will move in a
(a) Straight line (b) Circle
(c) Helix (d) Cycloid
Q.19 A 6.28m long wire is turned into a coil of diameter 0.2m
and a current of 1 amp is passed in it. The magnetic
induction at its centre will be -
(a) 6.28 × 10
–5
 T (b) 0 T
(c) 6.28 T (d) 6.28 × 10
–3 
T
DIRECTIONS (Q.20-Q.21) : In the following questions,
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.20Two long straight parallel wires carry
currents I
1
 and I
2
 respectively , in the same
direction (as shown). The distance
between the wires is R. The magnetic
field at the centre of the two wires will     
I
1 I
2
R
be-
(1)
0 12
(I I)
R
m-
p
 into the plane of paper (If I
1
 > I
2
)
(2)
0 21
(I I)
R
m-
p
 out of the plane of paper (if I
2
 > I
1
)
(3)
0 12
2
(I I)
R
m-
p
 out of the plane of paper (if I
2
 > I
1
)
(4)
0 21
2
(I I)
R
m-
p
 into the plane of paper (if I
1
 > I
2
)
Q.21 A wire of length L  carrying current I is bent into a circle
of one turn. The field at the center of the coil is B
1
. A
similar wire of length L carrying current I is bent into a
square of one turn. The field at its center is B
2
. Then
(1) B
1
 > B
2
(2)B
1
 = B
2
(3)
1
2
2
B
B
= (4)B
1
 < B
2
DIRECTIONS (Q.22-Q.24) : Read the passage given below
and answer the questions that follows :
A conducting wire is bent into a loop as shown in the figure. The
s e gme nt AOB is parabolic give n by the e quation y
2
 = 2x while
segment BA is a straight line parallel to the y-axis.
The magnetic field in the region is 
$
–8 Bk =
ur
 and the current in
the wire is 2A.
A
B
D
C
2 m
x
O
y
Q.22 The torque on the loop will be
(a) 162 Nm (b) 16 Nm
(c) 182 Nm (d) Zero
Q.23 The field created by the current in the loop at point C will be
(a)
$ 0
–
4
µ
k
p
(b)
$ 0
–
2
µ
k
p
(c)
$ 0
2
–
µ
k
p
(d) None of these
Page 4


DIRECTIONS (Q.1-Q.19) : There are 19 multiple choice
questions. Each question has 4 choices (a), (b), (c) and (d), out
of which ONLY ONE choice is correct.
Q.1 The magnitude of magnetic field at a point having
perpendicular distance 50 mm from a long straight
conducting wire carrying a current of 3A is
(a) 0.12 G (b) 1.2 G
(c) 12 G (d) 0.012 G
Q.2 A circular arc of wire of radius of curvature r subtends an
angle of  p/4 radian at its centre. If  i  current is  flowing in
it then the magnetic induction at its centre is -
(a)
0
i
8r
m
(b)
0
i
4r
m
(c)
0
i
16r
m
(d)0
Q.3 A current i is flowing in a conductor PQRST shaped as
shown in the figure. The radius of curved part QRS is r and
length of straight portions PQ and ST is very large. The
magnetic field at the centre O of the curved part  is -
90°
O
Q
R
r
i
P
T
x
y
z
i
S
(a)
0
µi 3
ˆ
1k
4r2
p éù
+
êú
p
ëû
(b)
0
µi 3
ˆ
1k
4r2
p éù
-
êú
pëû
(c)
0
µi 3
ˆ
1 ( k)
4r2
p éù
+-
êú
p
ëû
(d)
0
µi3
ˆ
1 ( k)
4r2
p éù
--
êú
pëû
2
DPP/ P 39
Q.4 Consider the loop PQRSP , carrying clockwise current i, shown
in the figure. The magnitude of magnetic field at the centre O of
the curved portion is
(a)
0
i
2r
m
p
 [p – f + tan f]
(b)
0
i
2r
m
p
R Q P
i i
S
O
r
f f
(
(c)0
(d)
0
i
2r
m
p
 [p – f + tan f]
Q.5 A circular coil of 0.2 m diameter has 100 turns and carries a
current of 0.1 ampere. The intensity of magnetic field at the
centre of the coil is -
(a) 6.28 × 10
–4
 N/A.m (b) 62.8 × 10
–4
 N/A.m
(c) 6.28 × 10
–5
 N/A.m (d) 62.8 × 10
–5
 N/A.m
Q.6 For the arrangement of two current carrying identical coils
shown in the figure, the magnetic field at the center O is
(N a nd a re pre se nt nu m be r o f turns and rad iu s of e a c h c oil)-
Coil-2
Coil-1
I
I
x
y
z
(a)
0
NI
2a
m
(b)
0
NI
2 2a
m
(c)
0
NI
2
m
(d)
0
NI
2a
m
Q.7 A current is flowing through a conducting hollow pipe
whose area of cross-section is shown in the fig. The value
of magnetic induction will be zero at-
(a) Point P, Q and R
• Q

R
P • (b) Point R but not at P and Q
(c) Point Q but not at P and R
(d) Point P but not at Q and R
Q.8 Dimensional formula of m
0
 is-
(a) MLT
–2 
A
–2
(b) MLT
–2
A
–2
(c) MLT
–2
 A
2
(d) MLT
2
 A
2
Q.9 A current of 1.0 ampere is flowing in the sides of an equilateral
triangle of side 4.5 × 10
–2
 m. Find the magnetic field at the
centroid of the triangle.
(Permeability constant m
0
 = 4p × 10
–7
 V-s/A-m).
(a) 4.0 × 10
–5
 weber/m
2
(b) 6.0 × 10
–8
 weber/m
2
(c) 2.0 × 10
–5
 weber/m
2
(d) 7.0 × 10
–12
 weber/m
2
Q.10 An air-solenoid has 500 turns of wire in its 40 cm length.
If the current in the wire be 1.0 ampere then the magnetic
field on the axis inside the solenoid is -
(a) 15.7 gauss (b) 1.57 gauss
(c) 0.157 gauss (d) 0.0157 gauss
Q.11 A solenoid of length 0.2m has 500 turns on it. If
8.71 × 10
–6
 Weber/m
2
 be the magnetic field at an end of
the solenoid, then the current flowing in the solenoid is –
(a)
0.174
p
A (b) 
0.0174
p
A (c)
17.4
p
A (d)
174
p
A
Q.12 A circular current carrying coil has a radius R. The distance
from the centre of the coil on the axis where the magnetic
induction will be 
1
8
th
 to its value at the centre of the coil,
is
(a)
R
3
(b) R3 (c)
2 3R
(d)
2
R
3
Q.13 The average radius of an air cored made toroid is 0.1 m
and it has 500 turns. If it carries 0.5 ampere current, then
the magnetic field inside it is :
(a) 5 × 10
–4
 tesla (b) 5 × 10
–3
 tesla
(c) 5 × 10
–2
 tesla (d) 2 × 10
–3
 tesla
Q.14The straight long conductors AOB and COD are
perpendicular to each other and carry current i
1
 and i
2
. The
magnitude of the magnetic induction at point P at a distance
a from the point O in a direction perpendicular to the plane
ACBD is
(a) ( )
0
12
µ
2pa
ii +
(b) ( )
0
12
µ
2pa
ii -
A
B
C D
i
1
i
2
B
1
B
2
P
O
a
(c) ( )
1/2
22 0
12
µ
2pa
ii +
(d)
( )
0 12
12
µ
2pa
ii
ii +
DPP/ P 39
3
Q.15 A conducting circular loop of radius r carries a constant
current i. It is placed in a uniform magnetic field B
ur
, such
that B
ur
 is perpendicular to the plane of the loop. The
magnetic force acting on the loop is
(a) ir B
ur
(b)2pri B
ur
(c) zero (d) pri B
ur
Q.16 The radius of a circular loop is r and a current i is flowing
in it. The equivalent magnetic moment will be
(a) ir (b) 2pir (c) ipr
2
(d)
2
1
r
Q.17 A current of 30 A is flowing in a vertical straight wire. If
the horizontal component of earth's magnetic field is 2 ×
10
–5
 tesla then the distance of null point from wire is -
(a) 0.9 m (b) 0.3 mm (c) 0.3 cm (d) 0.3 m
Q.18 A charged particle is released from rest in a region of steady
uniform electric and magnetic fields which are parallel to
each other. The particle will move in a
(a) Straight line (b) Circle
(c) Helix (d) Cycloid
Q.19 A 6.28m long wire is turned into a coil of diameter 0.2m
and a current of 1 amp is passed in it. The magnetic
induction at its centre will be -
(a) 6.28 × 10
–5
 T (b) 0 T
(c) 6.28 T (d) 6.28 × 10
–3 
T
DIRECTIONS (Q.20-Q.21) : In the following questions,
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.20Two long straight parallel wires carry
currents I
1
 and I
2
 respectively , in the same
direction (as shown). The distance
between the wires is R. The magnetic
field at the centre of the two wires will     
I
1 I
2
R
be-
(1)
0 12
(I I)
R
m-
p
 into the plane of paper (If I
1
 > I
2
)
(2)
0 21
(I I)
R
m-
p
 out of the plane of paper (if I
2
 > I
1
)
(3)
0 12
2
(I I)
R
m-
p
 out of the plane of paper (if I
2
 > I
1
)
(4)
0 21
2
(I I)
R
m-
p
 into the plane of paper (if I
1
 > I
2
)
Q.21 A wire of length L  carrying current I is bent into a circle
of one turn. The field at the center of the coil is B
1
. A
similar wire of length L carrying current I is bent into a
square of one turn. The field at its center is B
2
. Then
(1) B
1
 > B
2
(2)B
1
 = B
2
(3)
1
2
2
B
B
= (4)B
1
 < B
2
DIRECTIONS (Q.22-Q.24) : Read the passage given below
and answer the questions that follows :
A conducting wire is bent into a loop as shown in the figure. The
s e gme nt AOB is parabolic give n by the e quation y
2
 = 2x while
segment BA is a straight line parallel to the y-axis.
The magnetic field in the region is 
$
–8 Bk =
ur
 and the current in
the wire is 2A.
A
B
D
C
2 m
x
O
y
Q.22 The torque on the loop will be
(a) 162 Nm (b) 16 Nm
(c) 182 Nm (d) Zero
Q.23 The field created by the current in the loop at point C will be
(a)
$ 0
–
4
µ
k
p
(b)
$ 0
–
2
µ
k
p
(c)
$ 0
2
–
µ
k
p
(d) None of these
4
DPP/ P 39
Q.24 Magnetic field at point D due to segment AO of the loop is
directed parallel to
(a)
ˆ
k (b)
ˆ
k - (c)
ˆ
i
(d)
ˆ
j
DIRECTIONS (Q. 25-Q.27) : 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.25Statement -1: Cyclotron does not accelerate electron.
Statement-2: Mass of the electron is very small.
Q.26 Statement-1: The ion cannot move with a speed beyond a
certain limit in a cyclotron.
Statement-2: As velocity increases time taken by ion
increases.
Q.27Statement-1: If an electron, while coming vertically from
outerspace, enter the earth's magnetic field, it is deflected
towards west.
Statement-2: Electron has negative charge.