Moving Charges and Magnetism · Physics · NEET
MCQ (Single Correct Answer)
1
A tightly wound 100 turns coil of radius $$10 \mathrm{~cm}$$ carries a current of $$7 \mathrm{~A}$$. The magnitude of the magnetic field at the centre of the coil is (Take permeability of free space as $$4 \pi \times 10^{-7} \mathrm{SI}$$ units):
NEET 2024
2
A parallel plate capacitor is charged by connecting it to a battery through a resistor. If $$I$$ is the current in the circuit, then in the gap between the plates:
NEET 2024
3
A long straight wire of length $$2 \mathrm{~m}$$ and mass $$250 \mathrm{~g}$$ is suspended horizontally in a uniform horizontal magnetic field of $$0.7 \mathrm{~T}$$. The amount of current flowing through the wire will be $$\left(\mathrm{g}=9.8 \mathrm{~ms}^{-2}\right)$$ :
NEET 2023 Manipur
4
A uniform electric field and a uniform magnetic field are acting along the same direction in a certain region. If an electron is projected in the region such that its velocity is pointed along the direction of fields, then the electron:
NEET 2023 Manipur
5
A wire carrying a current $$I$$ along the positive $$\mathrm{x}$$-axis has length $$L$$. It is kept in a magnetic field $$\overrightarrow{\mathrm{B}}=(2 \hat{\mathrm{i}}+3 \hat{\mathrm{j}}-4 \hat{\mathrm{k}}) \mathrm{T}$$. The magnitude of the magnetic force acting on the wire is :
NEET 2023
6
A very long conducting wire is bent in a semi-circular shape from $$A$$ to $$B$$ as shown in figure. The magnetic field at point $$P$$ for steady current configuration is given by :
NEET 2023
7
A closely packed coil having 1000 turns has an average radius of 62.8 cm. If current carried by the wire of the coil is 1 A, the value of magnetic field produced at the centre of the coil will be (permeability of free space $$ = 4\pi \times {10^{ - 7}}$$ H/m) nearly
NEET 2022 Phase 2
8
The shape of the magnetic field lines due to an infinite long, straight current carrying conductor is
NEET 2022 Phase 2
9
Two very long, straight, parallel conductors A and B carry current of 5 A and 10 A respectively and are at a distance of 10 cm from each other. The direction of current in two conductors is same. The force acting per unit length between two conductors is : ($$\mu$$0 = 4$$\pi$$ $$\times$$ 10$$-$$7 SI unit)
NEET 2022 Phase 2
10
The magnetic field on the axis of a circular loop of radius 100 cm carrying current $$I = \sqrt 2 \,A$$, at point 1 m away from the centre of the loop is given by :
NEET 2022 Phase 2
11
A long solenoid of radius 1 mm has 100 turns per mm. If 1 A current flows in the solenoid, the magnetic field strength at the centre of the solenoid is
NEET 2022 Phase 1
12
Given below are two statements:
Statement I : Biot-Savart's law gives us the expression for the magnetic field strength of an infinitesimal current element (Idl) of a current carrying conductor only.
Statement II : Biot-Savart's law is analogous to Coulomb's inverse square law of charge q, with the former being related to the field produced by a scalar source, Idl while the latter being produced by a vector source, q.
In light of above statements choose the most appropriate answer from the options given below.
NEET 2022 Phase 1
13
From Ampere's circuital law for a long straight wire of circular cross-section carrying a steady current, the variation of magnetic field in the inside and outside region of the wire is
NEET 2022 Phase 1
14
A thick current carrying cable of radius 'R' carries current 'I' uniformly distributed across its cross section. The variation of magnetic field B(r) due to the cable with the distance 'r' from the axis of the cable is represented by :
NEET 2021
15
An infinitely long straight conductor carries a current of 5A as shown. An electron is moving with a speed of 105 m/s parallel to the conductor. The perpendicular distance between the electron and the conductor is 20cm at an instant. Calculate the magnitude of the force experienced by the electron at that instant.
NEET 2021
16
A long solenoid of 50 cm length having 100 turns carries a current of 2.5 A. The magnetic field at the centre of the solenoid is :
$$\left( {{\mu _0} = 4\pi \times {{10}^{ - 7}}Tm{{A}^{-1}}} \right)$$
$$\left( {{\mu _0} = 4\pi \times {{10}^{ - 7}}Tm{{A}^{-1}}} \right)$$
NEET 2020 Phase 1
17
Ionized hydrogen atoms and $$\alpha $$-particles with same momenta enters perpendicular to a constant magnetic field, B. The ratio of their radii of their paths rH : r$$\alpha $$ will be :
NEET 2019
18
A cylinderical conductor of radius R is carrying a constant current. The plot of the magnitude of the magnetic field. B with the distane d from the centre of the conductor, is correctly represented by the figure :
NEET 2019
19
A metallic rod of mass per unit length
0.5 kg m–1 is lying horizontally on a smooth
inclined plane which makes an angle of 30° with
the horizontal. The rod is not allowed to slide
down by flowing a current through it when a
magnetic field of induction 0.25 T is acting on it
in the vertical direction. The current flowing in
the rod to keep it stationary is
NEET 2018
20
Current sensitivity of a moving coil
galvanometer is 5 div/mA and its voltage
sensitivity (angular deflection per unit voltage
applied) is 20 div/V. The resistance of the
galvanometer is
NEET 2018
21
An arrangement of three parallel straight wires placed perpendicular to plane of paper carrying same current $$'I'$$ along the same direction as shown in fogure. Magnitude of force per unit length on the middle wire $$'B'$$ is given by
NEET 2017
22
An electron is moving in a circular path under the influence of a transverse magnetic field of 3.57 $$ \times $$ 10-2 T. If the value of e/m is 1.76 $$ \times $$ 1011 C kg$$-$$1, the frequency of revoluation of the electron is
NEET 2016 Phase 2
23
A long wire carrying a steady current is bent into a circular loop of one turn. The magnetic field at the centre of the loop is B. It is then bent into a circular coil of n turns. The magnetic field at the centre of this coil of n turns will be
NEET 2016 Phase 2
24
A square loop ABCD carrying a current $$i$$, is placed near and coplanar with a long straight conductor XY carrying a current $$I$$, the net force on the loop will be
NEET 2016 Phase 1
25
A long straight wire of radius $$a$$ carries a steady current $$I$$. The current is uniformly distributed over its cross-section. The ratio of the magnetic fields B and B', at radial distance $${a \over 2}$$ and 2$$a$$ respectively, from the axis of the wire is
NEET 2016 Phase 1
26
A proton and an alpha particle both enter a region of uniform magnetic field B, moving at right angles to the field B. If the radius of circular orbits for both the particles is equal and the kinetic energy acquired by proton is 1 MeV, the energy acquired by the alpha particle will be
AIPMT 2015
27
A wire carrying current $$I$$ has the shape shown in adjoining figure.
Linear parts of the wire are very long and parallel to X-axis while semicircular protion of radius R is lying in Y-Z plane. Magtnetic field at pont $$O$$ is
Linear parts of the wire are very long and parallel to X-axis while semicircular protion of radius R is lying in Y-Z plane. Magtnetic field at pont $$O$$ is
AIPMT 2015 Cancelled Paper
28
A conducting square frame of side 'a' and a long straight wire carrying current $$I$$ are located in the same plane as shown in the figure. The frame moves to the right with a constant velocity 'V'. The emf induced in the frame will be proportional to
AIPMT 2015 Cancelled Paper
29
An electron moving in a circular orbit of radius r makes n rotations per second. The magnetic field produced at the centre has magnitude
AIPMT 2015 Cancelled Paper
30
In an ammeter 0.2% of main current passes through the galvanometer. If resistance of galvanometer is G, the resistance of ammeter will be
AIPMT 2014
31
Two identical long conducting wires $$AOB$$ and $$COD$$ are placed at right angle to each other, with one above other such that $$O$$ is their common point for the two. The wires carry $$I$$1 and $$I$$2 currents, respectively. Point $$P$$ is lying at distance f from $$O$$ along a direction perpendicular to the plane containing the wires. The magnetic field at the point $$P$$ will be
AIPMT 2014
32
A circular coil ABCD carrying a current 'i' is placed in a uniform magnetic field. If the magnetic force on the segment AB is $$\overrightarrow F $$, the force on the remaining segment BCDA is
NEET 2013 (Karnataka)
33
A long straight wire carries a certain current and produces a magnetic field 2 $$ \times $$ 10$$-$$4 Wb m$$-$$2 at a perpendicular distance of 5 cm from the wire. An electron situated at 5 cm from the wire moves with a velocity 107 m/s towards the wire along perpendicular to it. The force experienced by the electron will be (charge on electron 1.6 $$ \times $$ 10$$-$$19 C)
NEET 2013 (Karnataka)
34
When a proton is released from rest in a room, it starts with an initial acceleration $$a$$0 towards west. When it is projected towards north with a speed $$v$$0 it moves with an initial acceleration 3$$a$$0 towards west. The an initial accelearation 3a0 towards west. The an initial acceleration 3$$a$$0 toward west. The electric and magnetic fields in the room are
NEET 2013
35
A proton carrying 1 MeV kinetic energy is moving in a circular path of radius R in uniform magnetic field. What should be the energy of an $$\alpha $$-particle to describe a circle of same radius in the same field?
AIPMT 2012 Mains
36
An alternating electric field, of frequency $$v$$, is applied across the does (radius = R) of a cyclotron that is being used to accelerate protons (mass = m). The operating magnetic field (B) used in the cyclotron and the kinetic energy (K) of the proton beam, produced by it, are given by
AIPMT 2012 Prelims
37
Two similar coils of radius R are lying concentrically with their planes at right angles to each other. The currents flowing in them are $$I$$ and 2$$I$$, respectively. The resultant magnetic field induction at the centre will be
AIPMT 2012 Prelims
38
A milli voltmeter of 25 milli volt range is to be converted into an ammeter of 25 ampare range. The value (in ohm) of neccessary shunt will be
AIPMT 2012 Prelims
39
A square loop, carrying a teady current $$I$$, is placed in a horizontal plane near a long straight conductor carrying a steady current $$I$$1 at a distance d from the conductor as shown in figure. The loop will experience
AIPMT 2011 Mains
40
Charge q is uniformly spread on a thin ring of radius R. The ring rotates about its axis with a uniform frequency $$f$$ Hz. The magnitude of magnetic induction at the center of the ring is
AIPMT 2011 Mains
41
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
AIPMT 2011 Mains
42
A current carrying closed loop in the form of a right angle isosceles triangle ABC is placed in uniform magnetic field acting along AB. If the magnetic force on the arm BC is $$\overrightarrow {F,} $$ the force on the arm AC is
AIPMT 2011 Prelims
43
A uniform electric field and a uniform magnetic field are acting along the same direction in a certain region. If an electron is projected in the region such that its velocity is pointed along the direction of fields, then the electron
AIPMT 2011 Prelims
44
A closely wound solenoid of 2000 turns and area of cross-section 1.5 $$ \times $$ 10$$-$$4 m2 carries a current of 2.0 A. It is suspended through its centre and perpendicular to its length, allowing it to turn in a horizontal plane in a uniform magnetic field 5 $$ \times $$ 10$$-$$2 tesla making an angle of 30o with the axis of the solenoid. The torque on the solenoid will be
AIPMT 2010 Mains
45
A particle having a mass of 10$$-$$2 kg carries a charge of 5 $$ \times $$ 10$$-$$8 C. The particle is given an initial horizontal velocity of 105 m s$$-$$1 in the presence of electric field $$\overrightarrow E $$ and magnetic field $$\overrightarrow B $$. To keep the particle moving in a horizontal direction, it is necessary that
(1) $$\overrightarrow B $$ should be perpendicular to the direction of velocity and $$\overrightarrow E $$ should be along the direction of velocity
(2) Both $$\overrightarrow B $$ and $$\overrightarrow E $$ should be along the direction of velocity
(3) Both $$\overrightarrow B $$ and $$\overrightarrow E $$ are mutually perpendicular and perpendicular to the direction of velocity.
(4) $$\overrightarrow B $$ should be along the direction of velocity and $$\overrightarrow E $$ should be perpendicular to the direction of velocity
Which one of the following pairs of statements is possible ?
(1) $$\overrightarrow B $$ should be perpendicular to the direction of velocity and $$\overrightarrow E $$ should be along the direction of velocity
(2) Both $$\overrightarrow B $$ and $$\overrightarrow E $$ should be along the direction of velocity
(3) Both $$\overrightarrow B $$ and $$\overrightarrow E $$ are mutually perpendicular and perpendicular to the direction of velocity.
(4) $$\overrightarrow B $$ should be along the direction of velocity and $$\overrightarrow E $$ should be perpendicular to the direction of velocity
Which one of the following pairs of statements is possible ?
AIPMT 2010 Mains
46
A current loop consists of two identical semicircular parts each of radius R, one lying in the x-y plane and the other in x-z plane. If the current in the loop is $$i$$. The resultant magnetic field due to the two semicircular parts at their common centre is
AIPMT 2010 Mains
47
A galvanometer has a coil of resistance 100 ohm and gives a full scale deflection for 30 mA current. If it is to work as a voltmeter of 30 volt range, the resistance required to be added will be
AIPMT 2010 Prelims
48
A square current carrying loop is suspended in a uniform magnetic field acting in the plane of the loop. If the force on one arm of the loop is the net force on the remaining three arms of the loop is
AIPMT 2010 Prelims
49
A galvanometer has a coil of resistance 100 ohm and gives a full scale deflection for 30 mA current. If it is to work as a voltmeter of 30 volt range, the resistance required to be added will be
AIPMT 2010 Prelims
50
Charge q is uniformly spread on a thin ring of radius R. The ring rotates about its axis with a uniform frequency $$f$$ Hz. The magnitude of magnetic induction at the center of the ring is
AIPMT 2010 Prelims
51
Under the influence of a uniform magnetic field, a charged particle moves with constant speed v in a circle of radius R. The time period of rotation of the particle
AIPMT 2009
52
The magnetic force acting on a charged particle of charge $$-$$2 $$\mu $$C in a magnetic frield of 2 T acting in y direction, when the particle velocity is $$\left( {2\widehat i + 3\widehat j} \right) \times {10^6}\,m{s^{ - 1}}$$
AIPMT 2009
53
A galvanometer havings a coil resistance of 60 $$\Omega $$ shows full scale deflection when a current of 1.0 amp passes through it. It can be converted into an ammeter to read currents upto 5.0 amp by
AIPMT 2009
54
A galvanometer of resistance 50 $$\Omega $$ is connected to a battery of 3 V along with a resistance of 2950 $$\Omega $$ in series. A full scale deflection of 30 divisions is obtained in the galvanometer. In order to reduce this deflection to 20 divisions, the resistance in series should be
AIPMT 2008
55
A closed loop PQRS carrying a current is placed in a uniform magnetic field. If the magnetic forces on segments PS, SR and RQ are F1, F2 and F3 respectively and are in the plane of the paper and along the directions shown, the force on the segment QP is
AIPMT 2008
56
A particle of mass m, charge Q and kinetic energy T enters a transverse uniform magnetic field of induction $$\overrightarrow B $$. After 3 seconds the kinetic energy of the particle will be
AIPMT 2008
57
The resistance of an ammeter is 13 $$\Omega $$ and its scale is graduated for a current upto 100 amps. After an additional shunt has been connected to this ammeter it becomes possible to measure currents upto 750 amperes by this meter. The value of shunt-resistance is
AIPMT 2007
58
Under the influence of a uniform magnetic field, a charged particle moves with constant speed v in a circle of radius R. The time period of rotation of the particle
AIPMT 2007
59
Two circular coils 1 and 2 are made from the same wire but the radius of the 1st coil is twice that of the 2nd coil. What is the ratio of potential difference in volts should be applied across them so that the magnetic field at their centres is the same?
AIPMT 2006
60
When a charged particle moving with velocity $$\overrightarrow v $$ is subjected to a magnetic field of induction $$\overrightarrow B $$, the force on it is non-zero. This implies that
AIPMT 2006
61
A very long straight wire carries a current $$I$$. At the instant when a charge +Q at point P has velocity $$\overrightarrow v $$, as shown, the force on the charge is
AIPMT 2005
62
An electron moves in a circular orbit with a uniform speed v. It producess a magnetic field B at the centre of the circle. The radius of the circle is proportional to
AIPMT 2005
63
To convert a galvanometer into a voltmeter one should connect a
AIPMT 2004
64
A galvanometer of 50 ohm resistance has 25 divisions. A current of 4 $$ \times $$ 10$$-$$4 ampere gives a deflection of one division. To convert this galvanometer into a voltmeter having a range of 25 volts, it should be connected with a resistance of
AIPMT 2004
65
A charged particle moves through a magnetic field in a firection perpendicular to it. Then the
AIPMT 2003
66
A long solenoid carrying a current producess a magnetic field B along its axis. If the current is doubled and the number of turns per cm is halved, the new value of the magnetic field is
AIPMT 2003
67
The magnetic field of given length of wire for single turn coil at its centre is B then its value for two turns coil for the same wire is
AIPMT 2002
68
A charge q moves in a region where electric field and magnetic field both exist, then force on it is
AIPMT 2002
69
To convert a galvanometer into a voltmeter one should connect a
AIPMT 2002
70
An electron having mass m and kinetic energy E anter in uniform magnetic field B perpendiculaly, then its frequency will be
AIPMT 2001
71
If number of turns, area and current through a coil is given by n, A and $$i$$ respectively then its magnetic moment will be
AIPMT 2001
72
The magnetic field at centre, P will be
AIPMT 2000