# JEE Advanced > Magnetic Effects of Current and Magnetism

Explore popular questions from Magnetic Effects of Current and Magnetism for JEE Advanced. This collection covers Magnetic Effects of Current and Magnetism previous year JEE Advanced questions hand picked by experienced teachers.

Physics
Chemistry
Mathematics
Q 1.

Correct4

Incorrect-1

A conducting circular loop of radius {tex} r {/tex} carries a constant current {tex} i . {/tex} It is placed in a uniform magnetic field {tex} \vec { B } _ { 0 } {/tex} such that {tex} \vec { B } _ { 0 } {/tex} is perpendicular to the plane of the loop. The magnetic force acting on the loop is

A

{tex} i r B _ { 0 } {/tex}

B

{tex} 2 \pi i r B _ { 0 } {/tex}

zero

D

{tex} \pi i r B _ { 0 } {/tex}

##### Explanation  Q 2.

Correct4

Incorrect-1

A battery is connected between two points {tex} A {/tex} and {tex} B {/tex} on the circumference of a uniform conducting ring of radius {tex} r {/tex} and resistance {tex} R {/tex}. One of the arcs {tex} A B {/tex} of the ring subtends an angle {tex} \theta {/tex} at the centre. The value of the magnetic induction at the centre due to the current in the ring is

A

proportional to {tex} 2 \left( \mathrm{180 ^ { \circ } - \theta} \right) {/tex}

B

inversely proportional to {tex} \mathrm { r } {/tex}

C

zero, only if {tex}\mathrm { \theta = 180 ^ { \circ }} {/tex}

zero for all values of {tex} \theta {/tex}

##### Explanation  Q 3.

Correct4

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A proton, a deuteron and an {tex} \alpha {/tex} - particle having the same kinetic energy are moving in circular trajectories in a constant magnetic field. If {tex} r _ { p } , r _ { d } , {/tex} and {tex} r _ { \alpha } {/tex} denote respectively the radii of the trajectories of these particles, then

{tex} r _ { \alpha } = r _ { p } < r _ { d } {/tex}

B

{tex} r _ { \alpha } > r _ { \mathrm { d } } > r _ { \mathrm { p } } {/tex}

C

{tex} r _ { \alpha } = r _ { d } > r _ { p } {/tex}

D

{tex} r _ { p } = r _ { d } = r _ { \alpha } {/tex}

##### Explanation Q 4.

Correct4

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A charged particle is released from rest in a region of steady and uniform electric and magnetic fields which are parallel to each other. The particle will move in a

straight line

B

circle

C

helix

D

cycloid

##### Explanation  Q 5.

Correct4

Incorrect-1

A particle of charge {tex} q {/tex} and mass {tex} m {/tex} moves in a circular orbit of radius r with angular speed {tex} \omega {/tex}. The ratio of the magnitude of its magnetic moment to that of its angular momentum depends on

A

{tex} \omega {/tex} and {tex} q {/tex}

B

{tex} \omega , q {/tex} and {tex} m {/tex}

{tex} q {/tex} and {tex} m {/tex}

D

{tex} w {/tex} and {tex} m {/tex}

##### Explanation Q 6.

Correct4

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An infinitely long conductor {tex} P Q R {/tex} is bent to form a right angle as shown in Figure. A current {tex} I {/tex} flows through {tex} P Q R {/tex}. The magnetic field due to this current at the point {tex} M {/tex} is {tex} H _ { 1 } {/tex}. Now, another infinitely long straight conductor {tex} Q S {/tex} is connected at {tex} Q {/tex} so that current is {tex} I / 2 {/tex} in {tex} Q R {/tex} as well as in {tex} Q S , {/tex} the current in {tex} P Q {/tex} remaining unchanged. The magnetic field at {tex} M {/tex} is now {tex} H _ { 2 } . {/tex} The ratio {tex} H _ { 1 } / H _ { 2 } {/tex} is given by A

{tex} 1 / 2 {/tex}

B

{tex}1{/tex}

{tex} 2 / 3 {/tex}

D

{tex}2{/tex}

##### Explanation  Q 7.

Correct4

Incorrect-1

An ionized gas contains both positive and negative ions. If it is subjected simultaneously to an electric field along the {tex} + x {/tex} -direction and a magnetic field along the {tex} + z {/tex} -direction, then

A

positive ions deflect towards {tex} + y {/tex} -direction and negative ions towards {tex} - y {/tex} direction

B

all ions deflect towards {tex} + y {/tex} -direction

all ions deflect towards {tex} - y {/tex} -direction

D

positive ions deflect towards {tex}- y-{/tex} direction and negative ions towards {tex} + y {/tex} -direction.

##### Explanation  Q 8.

Correct4

Incorrect-1

A non-planar loop of conducting wire carrying a current {tex} I {/tex} is placed as shown in the figure. Each of the straight sections of the loop is of length {tex} 2 a {/tex}. The magnetic field due to this loop at the point {tex} P ( a , 0 , a ) {/tex} points in the direction A

{tex} \frac { 1 } { \sqrt { 2 } } ( - \hat { j } + \hat { k } ) {/tex}

B

{tex} \frac { 1 } { \sqrt { 3 } } ( - \hat { j } + \hat { k } + \hat { i } ) {/tex}

C

{tex} \frac { 1 } { \sqrt { 3 } } ( \hat { i } + \hat { j } + \hat { k } ) {/tex}

{tex} \frac { 1 } { \sqrt { 2 } } ( \hat { i } + \hat { k } ) {/tex}

##### Explanation   Q 9.

Correct4

Incorrect-1

Two particles {tex} A {/tex} and {tex} B {/tex} of masses {tex} m _ { A } {/tex} and {tex} m _ { B } {/tex} respectively and having the same charge are moving in a plane. A uniform magnetic field exists perpendicular to this plane. The speeds of the particles are {tex} v _ { A } {/tex} and {tex} v _ { B } {/tex} respectively and the trajectories are as shown in the figure. Then A

{tex} m _ { A } \mathrm { v } _ { A } < m _ { B } \mathrm { v } _ { B } {/tex}

{tex} m _ { A } v _ { A } > m _ { B } v _ { B } {/tex}

C

{tex} m _ { A } < m _ { B } {/tex} and {tex} v _ { A } < v _ { B } {/tex}

D

{tex} m _ { A } = m _ { B } {/tex} and {tex} v _ { A } = v _ { B } {/tex}

##### Explanation Q 10.

Correct4

Incorrect-1

A coil having {tex} N {/tex} turns is wound tightly in the form of a spiral with inner and outer radii {tex} a {/tex} and {tex} b {/tex} respectively. When a current {tex} I {/tex} passes through the coil, the magnetic field at the center is

A

{tex} \frac { \mu _ { o } N I } { b } {/tex}

B

{tex} \frac { 2 \mu _ { o } N I } { a } {/tex}

{tex} \frac { 2 \mu _ { o } N I } { 2 ( b - a ) } \ln \frac { b } { a } {/tex}

D

{tex} \frac { 2 \mu _ { o } N I } { 2 ( b - a ) } \ln \frac { a } { b } {/tex}

##### Explanation  Q 11.

Correct4

Incorrect-1

The magnetic field lines due to a bar magnet are correctly shown in

A B C  ##### Explanation Q 12.

Correct4

Incorrect-1

An electron travelling with a speed u along the positive {tex} x - {/tex} axis enters into a region of magnetic field where {tex} B = - B _ { 0 } \hat { k } {/tex} {tex} ( x /> 0 ) . {/tex} It comes out of the region with speed v then A

{tex} v = u {/tex} at {tex} y > 0 {/tex}

{tex} v = u {/tex} at {tex} y < 0 {/tex}

C

{tex} v > u {/tex} at {tex} y > 0 {/tex}

D

{tex} v > u {/tex} at {tex} y < 0 {/tex}

##### Explanation Q 13.

Correct4

Incorrect-1

A magnetic field {tex} \vec { B } = B _ { 0 } \hat { J } , {/tex} exists in the region a {tex} < x < 2 a {/tex}, and {tex} \bar { B } = - B _ { 0 } \hat { j } , {/tex} in the region {tex} 2 a < x < 3 a {/tex}, where {tex} B _ { 0 } {/tex} is a positive constant. A positive point charge moving with a velocity {tex} \vec { v } = v _ { 0 } \hat { i } , {/tex} where {tex} v _ { 0 } {/tex} is a positive constant, enters the magnetic field at {tex} x = a . {/tex} The trajectory of the charge in this region can be like  B C D ##### Explanation Q 14.

Correct4

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A thin flexible wire of length {tex} L {/tex} is connected to two adjacent fixed points and carries a current I in the clockwise direction, as shown in the figure. When the system is put in a uniform magnetic field of strength {tex} B {/tex} going into the plane of the paper, the wire takes the shape of a circle. The tension in the wire is A

{tex} I B L {/tex}

B

{tex} \frac { I B L } { \pi } {/tex}

{tex} \frac { I B L } { 2 \pi } {/tex}

D

{tex} \frac { I B L } { 4 \pi } {/tex}

##### Explanation  Q 15.

Correct4

Incorrect-1

A long insulated copper wire is closely wound as a spiral of {tex} ^ { \prime } N ^ { \prime } {/tex} turns. The spiral has inner radius {tex} ^ { \prime } a ^ { \prime } {/tex} and outer radius {tex} ^ { \prime } b ^ { \prime } . {/tex} The spiral lies in the {tex}XY{/tex} plane and a steady current {tex} ^ { \prime } I ^{\prime} {/tex} flows through the wire. The {tex}Z{/tex}-component of the magnetic field at the centre of the spiral is {tex} \frac { m _ { 0 } N I } { 2 ( b - a ) } \ell n \left( \frac { b } { a } \right) {/tex}

B

{tex} \frac { m _ { 0 } N I } { 2 ( b - a ) } \ell n \left( \frac { b + a } { b - a } \right) {/tex}

C

{tex} \frac { m _ { 0 } N I } { 2 b } \ell n \left( \frac { b } { a } \right) {/tex}

D

{tex} \frac { m _ { 0 } N I } { 2 b } \ln \left( \frac { b + a } { b - a } \right) {/tex}

Q 16.

Correct4

Incorrect-1

An infinitely long hollow conducting cylinder with inner radius {tex} R / 2 {/tex} and outer radius {tex} R {/tex} carries a uniform current density along its length. The magnitude of the magnetic field, {tex} | \vec { B } | {/tex} as a function of the radial distance {tex} r {/tex} from the axis is best represented by

A B C  ##### Explanation  Q 17.

Correct4

Incorrect-1

A symmetric shaped conducting wire loop is carrying a steady state current {tex}I{/tex} as shown in the figure. The distance between the diametrically opposite vertices of the star is {tex}4a{/tex}. The magnitude of the magnetic field at the center of the loop is {tex} \frac { \mu _ { 0 } l } { 4 \pi a } 6 [ \sqrt { 3 } - 1 ] {/tex}

B

{tex} \frac { \mu _ { 0 } 1 } { 4 \pi \mathrm { a } } 6 [ \sqrt { 3 } + 1 ] {/tex}

C

{tex} \frac { \mu _ { 0 } l } { 4 \pi a } 3 [ \sqrt { 3 } - 1 ] {/tex}

D

{tex} \frac { \mu _ { 0 } l } { 4 \pi a } 3 [ 2 - \sqrt { 3 } ] {/tex}

##### Explanation  