Magnetic Effects of Current and Magnetism — DPP 3

20 NEET questions from Magnetic Effects of Current and Magnetism, with answers and explanations. Attempt it as a timed test to get scoring, accuracy breakdown and mistake tracking.

Attempt this test free 20 questions · 30 minutes · +80 marks
1
Which of the following statement is not true; magnetic field at the centre of current carrying loop :-
  1. A proportional to current
  2. B inversely proportional to radius
  3. C proportional to number of turns
  4. D none
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Correct answer: D

2
A very long straight wire carries a current I. At the instant when a charge +Q at point P has velocity $\vec { v }$, as shown, the magnetic force on the charge is:-
Magnetic Effects of Current and Magnetism – NEET-9371
  1. A along ox
  2. B opposite to oy
  3. C along oy
  4. D opposite to ox
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Correct answer: C

Magnetic Effects of Current and Magnetism – NEET-9371
3
A current carrying wire is arranged at any angle in an uniform magnetic field, then
  1. A only force acts on wire
  2. B only torque acts on wire
  3. C both
  4. D none
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Correct answer: A

4
When a charged particle enters in a uniform magnetic field its kinetic energy :-
  1. A remains constant
  2. B increases
  3. C decreases
  4. D becomes zero
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Correct answer: A

Kinetic energy of charge particle is always constant, if it enters perpendicular in uniform magnetic field.
5
A current carrying wire AC is placed in uniform transverse magnetic field then the force on wire AC:-
Magnetic Effects of Current and Magnetism – NEET-9391
  1. A 3 N
  2. B 4.2 N
  3. C 6 N
  4. D 4 N
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Correct answer: A

Magnetic Effects of Current and Magnetism – NEET-9391
6
Two parallel wires in free space are 10 cm apart and each carries a current of 10 A in the same direction. The magnetic force per unit length of each wire is :-
  1. A $2 \times 10 ^ { - 4 } \mathrm {~N}$, attractive
  2. B $2 \times 10 ^ { - 4 } \mathrm {~N}$, repulsive
  3. C $2 \times 10 ^ { - 7 } \mathrm {~N}$, attractive
  4. D $2 \times 10 ^ { - 7 } \mathrm {~N}$, repulsive
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Correct answer: A

Magnetic Effects of Current and Magnetism – NEET-9394
7
In a region constant uniform electric and magnetic field is present. Both field are parallel. In this region a charge released from rest, then path of particle is :-
  1. A Circle
  2. B Helical
  3. C Straight line
  4. D Ellipse
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Correct answer: C

8
A rectangular loop carrying a current $i _ { 1 }$, is situated near a long straight wire carrying a steady current $\mathrm { i } _ { 2 }$. The wire is parallel to one of the sides of the loop and is in the plane of the loop as shown in the figure. Then the current loop will :-
Magnetic Effects of Current and Magnetism – NEET-9397
  1. A move away from the wire
  2. B move towards the wire.
  3. C remain stationary.
  4. D rotate about an axis parallel to the wire.
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Correct answer: B

9
An electron is moving in a circle of radius $5.1 \times 10 ^ { - 11 } \mathrm {~m}$ at a frequency of $6.8 \times 10 ^ { 15 } \mathrm { rev } . / \mathrm { sec }$. The equivalent current is approximately :-
  1. A $5.1 \times 10 ^ { - 3 } \mathrm {~A}$
  2. B $6.8 \times 10 ^ { - 3 } \mathrm {~A}$
  3. C $1.1 \times 10 ^ { - 3 } \mathrm {~A}$
  4. D $2.2 \times 10 ^ { - 3 } \mathrm {~A}$
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Correct answer: C

I = ef
10
A magnetic field :-
  1. A Always exerts a force on charged particle
  2. B Never exerts a force on charged particle
  3. C Exert a force, if the charged particle is moving across the magnetic field line
  4. D Exerts a force, if the charged particle is moving along the magnetic field line
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Correct answer: C

11
Two parallel beams of positrons moving in the same direction will :-
  1. A Repel to each other
  2. B Will not interact with each other
  3. C Attract to each other
  4. D Be deflected normal to the plane containing the two beams
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Correct answer: A

12
A proton and an α-particle moving with the same velocity and enter into a uniform magnetic field which is acting normal to the plane of their motion. The ratio of the radii of the circular paths described by the proton and α-particle respectively :-
  1. A 1 : 2
  2. B 1 : 4
  3. C 1 : 16
  4. D 4 : 1
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Correct answer: A

13
A wire PQ carries a current 'i' is placed perpendicular to a long wire XY carrying a current I. The direction of force on PQ will be:-
Magnetic Effects of Current and Magnetism – NEET-9390
  1. A towards right
  2. B towards left
  3. C upwards
  4. D downwards
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Correct answer: D

14
2A current is flowing in a circular loop of radius 1 m. Magnitude of magnetic field at the centre of circular loop will be :-
  1. A $\frac { \mu _ { 0 } } { 2 }$
  2. B $2 \mu _ { 0 }$
  3. C $\mu _ { 0 }$
  4. D $\frac { \mu _ { 0 } } { 2 \pi }$
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Correct answer: C

15
Current I is flowing in a conducting circular loop of radius R. It is kept in a magnetic field B which is perpendicular to the plane of circular loop, the magnetic force acting on the loop is :-
  1. A IRB
  2. B $2 \pi \mathrm { IRB }$
  3. C Zero
  4. D $\pi \mathrm { IRB }$
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Correct answer: C

16
Force exist on a current carrying wire which is placed in external magnetic field, due to :-
  1. A free electrons in wire
  2. B free positive ions in wire
  3. C Both (A) & (B)
  4. D None
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Correct answer: A

17
A charged particle moves through a magnetic field in a direction perpendicular to it. Then the :-
  1. A speed of the particle remains unchanged
  2. B direction of motion of particle remains unchanged
  3. C acceleration of particle remains unchanged
  4. D velocity of particle remains unchanged
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Correct answer: A

18
A current of $1 / 4 \pi$ ampere is flowing through a toroid. It has 1000 number of turn per meter then value of magnetic field (in Wb/m$^{2}$) along its axis is :-
  1. A $10 ^ { - 2 }$
  2. B $10 ^ { - 3 }$
  3. C $10 ^ { - 4 }$
  4. D $10 ^ { - 7 }$
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Correct answer: C

Magnetic Effects of Current and Magnetism – NEET-9341
19
A charge 'q' moves in a region where electric field and magnetic field both exist, then force on it:-
  1. A $\mathrm { q } ( \overrightarrow { \mathrm { v } } \times \overrightarrow { \mathrm { B } } )$
  2. B $\mathrm { q } \overrightarrow { \mathrm { E } } + \mathrm { q } ( \overrightarrow { \mathrm { v } } \times \overrightarrow { \mathrm { B } } )$
  3. C $q \vec { E } + q ( \vec { B } \times \vec { v } )$
  4. D $\mathrm { q } \overrightarrow { \mathrm { B } } + \mathrm { q } ( \overrightarrow { \mathrm { E } } \times \overrightarrow { \mathrm { v } } )$
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Correct answer: B

20
A closely wound flat circular coil of 25 turns of wire has diameter of 10 cm and carries a current of 4 ampere. Determine the magnetic flux density at the centre of the coil :-
  1. A $1.679 \times 10 ^ { - 5 } \mathrm {~T}$
  2. B $2.028 \times 10 ^ { - 4 } \mathrm {~T}$
  3. C $1.257 \times 10 ^ { - 3 } \mathrm {~T}$
  4. D $1.512 \times 10 ^ { - 6 } \mathrm {~T}$
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Correct answer: C

$B=\frac{\mu_{0} N i}{2 R}$

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