Top of Pyramid - Test #57- Moving Charges &

Magnetism Contact Number: 9667591930 / 8527521718

1.
An electron is traveling along the x-direction. It
What is the net force on the square coil ? encounters a magnetic field in the y-direction. Its
subsequent motion will be

1. Straight-line along the x-direction

2. A circle in the xz-plane
3. A circle in the yz-plane
4. A circle in the xy-plane

(a) 25 × 10 −7
N moving towards wire
6.
(b) 25 × 10 −7
N moving away from wire
A closed-loop (Of any shape) carrying current is lying in
(c) 35 × 10 −7
N moving towards wire the x-y plane. A uniform magnetic field B is present in
the region such that the loop experiences zero force :
(d) 35 × 10 −7
N moving away from wire
2. 1. B acts along the x-axis

A current carrying closed loop in the form of a right 2. B acts along the y-axis
angle isosceles triangle ABC is placed in a uniform 3. B acts along the z-axis
magnetic field acting along AB. If the magnetic force on
the arm BC is F, the force on the arm AC is 4. B can any of the above direction for the net force to be
zero

7.
A circular coil of wire of radius 'r' has 'n' turns and
carries a current 'I'. The magnetic induction (B) at a point
on the axis of the coil at a distance √3r from its center is
:
(a) −F (b) F 1.
μ0 In

4r

(c) √2F (d) −√2F μ0 In

2. 8r

3.
μ0 In
3.
Order of q/m ratio of proton, α-particle and electron is 16r

μ0 In
4.
(a) e > p > α (b) p > α > e 32r

(c) e > α > p (d) None of these 8.

4. The dots in the figure show a magnetic field

perpendicular to the plane of the paper and coming out of
When an electron enters perpendicularly in a magnetic it. The curve ABC shows the trajectory of a particle in
field with velocity v, time period of its revolution is T. If the plane of the paper. What is the particle?
it enters in the same magnetic field with a velocity 2v,
then its time period will be
1. 2T
2. 4T
3. T

4. T
1. Proton
5. Page: 1
 Top of Pyramid - Test #57- Moving Charges &
Magnetism Contact Number: 9667591930 / 8527521718

3. Neutron (d) At points halfway between the wires in the horizontal

plane
4. It cannot be predicted
13.
9.
In the figure, shown the magnetic induction at the centre
If electron of velocity ˆ ˆ
(2 i + 3 i ) is subjected to a of the arc due to the current in portion AB will be
magnetic field 4k̂ then
1. Speed will change
2. Direction will change
3. Both (1) and (2)
μ0 i μ0 i

4. None of the above (a) r

(c) 4r

10. (b)
μ0 i
(d) Zero
2r

Below figures (1) and (2) represent lines of force. Which 14.
is correct statement ?
In a current carrying long solenoid, the field produced
does not depend upon :

(a) Number of turns per unit length

(b) Current flowing
(c) Radius of the solenoid
(1) Figure (1) represents magnetic lines of force
(d) All of the above three
(2) Figure (2) represents magnetic lines of force
15.
(3) Figure (1) represents electric lines of force
In an ammeter 0.2% of main current passes through the
(4) Both figure (1) and figure (2) represent magnetic lines galvanometer. If resistance of galvanometer is G, the
of force resistance of ammeter will be
11.
(a) 1
G
The magnetic induction at a point P which is distant 4 cm 499

from a long current carrying wire is 10 Tesla . The

−8

field of induction at a distance 12 cm from the same (b)

499
G
500

current would be :
(c) 1
G
(a) 3. 33 × 10 Tesla
−9
(b) 1.11×10 −4
500

Tesla (d) 500

G
(c) 3 × 10 −3
Tesla (d) 9 × 10 −2 499

Tesla 16.
12. The current is flowing in south direction along a power
line. The direction of magnetic field above the power line
Two straight horizontal parallel wires are carrying the
(neglecting earth's field) is :
same current in the same direction, d is the distance
between the wires. You are provided with a small freely
(a) South (b) East
suspended magnetic needle. At which of the following
positions will the orientation of the needle be (c) North (d) West
independent of the magnitude of the current in the wires
17.
(a) At a distance d/2 from any of the wires in any plane
An electron and a proton with equal momentum enter
(b) At a distance d/2 from any of the wires in the perpendicularly into a uniform magnetic field, then :
horizontal plane
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 Top of Pyramid - Test #57- Moving Charges &
Magnetism Contact Number: 9667591930 / 8527521718

22.
(b) The path of proton shall be less curved than that of
electron A small coil of N turns has an effective area A and carries
a current I. It is suspended in a horizontal magnetic field
(c) Both are equally curved . .

B such that its plane is perpendicular to B. The work

(d) Path of both will be straight line done in rotating it by 180° about the vertical axis is
18. (a) N AI B (b) 2N AI B
Two particles A and B of masses m and m (c) 2πNAIB A B (d) 4πN AI B
respectively and having the same type of charge are
moving in a plane. A uniform magnetic field exists 23.
perpendicular to this plane. The speeds of the particles The sensitivity of a moving coil galvanometer can be
are v and v respectively, and the trajectories are as increased by decreasing
A B

shown in the figure. Then

(a) The number of turns in the coil
(b) The area of the coil
(c) The magnetic field
(d) The couple per unit twist of the suspension
(a) m A vA < m B vB (b) 24.
m A vA > m B vB
An electron, moving in a uniform magnetic field of
−
⇀
(c) mA < mB and vA < vB (d) induction of intensity B, has its radius directly
mA = mB and vA = vB proportional to :
19.
(a) Its charge (b) Magnetic field
An electric current passes through a long straight wire.
At a distance 5 cm from the wire, the magnetic field is B. (c) Speed (d) None of these
The field at 20 cm from the wire would be : 25.
(a) B

6
(b) B

4
A particle of charge q and mass m is moving along the x-
axis with a velocity v and enters a region of electric field
(c) B

3
(d) B

2
E and magnetic field B as shown in the figure below. For
which figure the net force on the charge may be zero?

20.
Two particles X and Y having equal charges, after being
accelerated through the same potential difference, enter a
region of uniform magnetic field and describes circular
path of radius R and R respectively. The ratio of mass
1 2

of X to that of Y is :
1/2

(a) (b)
R1 R2
( )
R2 R1

2
R1 R1
(c) (
R2
) (d) R2
26.
21.
A long straight wire along the z-axis carries a current I in
Two thin long parallel wires separated by a distance b are →
the negative z-direction. The magnetic field vector B at
carrying a current i amp each. The magnitude of the force a point having coordinates (x, y) in the z = 0 plane is :
per unit length exerted by one wire on the other is
ˆ ˆ
μ0 I(y i −x j )

μ0 i
2
μ0 i
2
(a)
(a) b
2
(b) 2πb
2
2π(x +y )
2

Page: 3
 Top of Pyramid - Test #57- Moving Charges &
Magnetism Contact Number: 9667591930 / 8527521718

μ0 μ0
(a) (b)
ˆ ˆ i π i π
μ0 I(x j −y i ) ˆ ˆ
(2 − )j (2 + )j
(c) 2
2π(x +y )
2
4π a 2 4π a 2

(c) (d)
μ0 μ0
i π ˆ i π ˆ
μ0 I(x î −y ĵ )
(2 + )i (2 + )k
4π a 2 4π a 2

(d) 2
2π(x +y )
2

30.
27.
An elastic circular wire of length L carries a current I. It
Figure shows a square loop ABCD with edge length a. →
is placed in a uniform magnetic field B (out of paper)
The resistance of the wire ABC is r and that of ADC is 2r. →
The value of magnetic field at the centre of the loop such that its plane is perpendicular to the direction of B .
assuming uniform wire is The wire will experience

(a) No force (b) A stretching force

√2μ i √2μ i
(a) 0
⊙ (b) 0
⊗
3πa 3πa
(c) A compressive force (d) A torque
31.
√2μ0 i √2μ0 i
(c) πa
⊙ (d) πa
⊗

28. Two particles each of mass m and charge q are attached

to the two ends of a light rigid rod of length 2R. The rod
A particle with charge q, moving with a momentum p, is rotated at constant angular speed about a perpendicular
enters a uniform magnetic field normally. The magnetic axis passing through its centre. The ratio of the
field has magnitude B and is confined to a region of magnitudes of the magnetic moment of the system and its
width d, where d < , The particle is deflected by an
p

Bq
angular momentum about the centre of the rod is
angle θ in crossing the field (a)
q
(b)
q

2m m

2q
(c) (d)
q

m πm

32.
Three long, straight parallel wires carrying current, are
arranged as shown in figure. The force experienced by a
25 cm length of wire C is

(a) sin θ = (b) sin θ =

Bqd p

p Bqd

Bp
(c) sin θ = (d) sin θ =
pd

qd Bq

29.

The unit vectors ˆi , ˆj and k

ˆ
are as shown below. What
will be the magnetic field at O in the following figure? (a) 10 −3
N

(b) 2. 5 × 10 −3
N

(c) Zero
(d) 1. 5 × 10 −3
N

33.
Page: 4
When a proton is released from rest in a room, it
 Top of Pyramid - Test #57- Moving Charges &
Magnetism Contact Number: 9667591930 / 8527521718

starts with an initial acceleration a towards west. When

o A galvanometer of 50Ω resistance has 25 divisions. A
it is projected towards north with a speed v , it moves
o current of 4 × 10 gives a deflection of one division. To
−4

with an initial acceleration 3a towards west. The electric

o convert this galvanometer into a voltmeter having a range
and magnetic fields in the room are of 25 V, it should be connected with a resistance of

(a) mao/e west, 4mao/evo up 1. 245Ω as a shunt

2. 2550Ω in series
(b) mao/e west, 2mao/evo down
3. 2450Ω in series
(c) mao/e east, 3mao/evo up 4. 2550Ω as a shunt
38.
(d) mao/e east, 3mao/evo down
→
When a charged particle moving with velocity v is
→
subjected to a magnetic field of induction B , the force
34. on it is non-zero. This implies the
→
Two wires are held perpendicular to the plane at 5m 1. angle between
→
v and B is necessary 90°.
apart. They carry currents of 2.5 A and 5A in same
→
direction. Then the magnetic field strength (B) at a point 2. angle between
→
v and B can have any value other
midway between the wires will be - than 90°.
μ0 T
1. T →
→
4π
3. angle between v and B can have any other value
2.
μ0
T
than zero and 180°.
2π

→
→
3.
3μ0
T
4. angles between v and B is either zero or 180°.
2π

3μ0
39.
4. T

A galvanometer having a coil resistance of 60Ω shows

4π

35. full scale deflection when a current of 1.0 A passes

through it. It can be converted into an ammeter to read
An electron moves with a velocity 1 × 10 m s in a
3 −1

current up to 5.0A by
magnetic field of induction 0.3 T at an angle 30°. If e

of electron is 1. 76 × 10 C kg , the radius of the path

11 −1 1. putting in series a resistance of 15Ω.
is nearly 2. putting in series a resistance of 240Ω.
1. 10 m 8

3. putting in parallel a resistance of 15Ω.

2. 2 × 10 m −8
4. putting in parallel a resistance of 240Ω.
3. 10 m −8
40.
4. 10 −10
m A galvanometer has a coil of resistance 100 ohm and
gives a full scale deflection for a 30 mA current. If it is
36.
used as a voltmeter of 30 volt range, the resistance
A charged particle of charge q and mass m enters required to be added will be
→
perpendicularly in a magnetic field B . Kinetic energy of 1. 1000Ω
the particle is E; then frequency of rotation is
2. 900Ω
qB
1. mπ 3. 1800Ω
qB
2. 2πm
4. 500Ω
qBE 41.
3. 2πm

qB
A current loop consists of two identical semicircular
4. parts each of radius R, one lying in the x-y plane and the
2πE
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 Top of Pyramid - Test #57- Moving Charges &
Magnetism Contact Number: 9667591930 / 8527521718

at their common center is

μ0 i
1. 2R

μ0 i
2. 4R

μ0 i
3.
√2R

μ0 i
4.
2μ0 I i
1. 3π
2√2R

42.
μ0 I i
2. 2π

Charge q is uniformly spread on a thin ring of radius R.

3.
2μ0 I i

The ring rotates about its axis with a uniform frequency f 3πL

Hz. The magnitude of magnetic induction of the centre of μ0 I i

the ring is 4. 2πL

μ0 qf
1. 2πR
Fill OMR Sheet
μ0 qf
2. 2R

3.
μ0 q

2 fR

4.
μ0 q

2πfR

43.
A galvanometer of resistance, G, is shunted by a
resistance S ohm. To keep the main current in the circuit
unchanged, the resistance to be put in series with the
galvanometer is

1. G

(S+G)

2. S

(S+G)

3. SG

(S+G)

4. G

(S+G)

44.
An electron moving in a circular orbit of radius r makes n
rotations per second. The magnetic field produced at the
centre has magnitude
1. zero
2
μ0 π e
2. r

3.
μ0 ne

2r

μ0 ne
4. 2πr

45.
A square loop ABCD carrying a current i is placed near
coplanar long straight conductor XY carrying a current I.
The net force on the loop will be - Page: 6
 Top of Pyramid - Test #57- Moving Charges &
Magnetism Contact Number: 9667591930 / 8527521718

Page: 7