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

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Magnetic Effects of Current and Magnetism

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Q 1. A solenoid of {tex} 1.5 \ metre {/tex} length and {tex} 4.0 \ cm {/tex} diameter posses {tex}10{/tex} turn per {tex} c m . {/tex} A current of {tex}5\ ampere{/tex} is flowing through it. The magnetic induction at axis inside the solenoid is

{tex} 2 \pi \times 10 ^ { - 3 } {/tex} Tesla

B

{tex} 2 \pi \times 10 ^ { - 5 } {/tex} Tesla

C

{tex} 4 \pi \times 10 ^ { - 2 } {/tex} Gauss

D

{tex} 2 \pi \times 10 ^ { - 5 } {/tex} Gauss

Explanation

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Q 2. The line on earth's surface joining the points where the earth's magnetic field is horizontal is called

A

Magnetic meridian

B

Magnetic axis

C

Magnetic line

Magnetic equator

Explanation

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Q 3. The magnetic induction field at the centre {tex} C {/tex} of the arrangement shown in Fig. 15.38 is

{tex} \frac { \mu _ { 0 } I} { 4 \pi r } ( 1 + \pi ) {/tex}

B

{tex} \frac { \mu _ { 0 } I} { 2 \pi r } ( 1 + \pi ) {/tex}

C

{tex} \frac { \mu _ { 0 } I } { \pi r } ( 1 + \pi ) {/tex}

D

{tex} \frac { \mu _ { 0 } I } { r } ( 1 + \pi ) {/tex}

Explanation

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Q 4. Curie temperature is the temperature above which

A

a paramagnetic material becomes diamagnetic.

B

a ferromagnetic material becomes diamagnetic.

C

a paramagnetic material becomes ferromagnetic.

a ferromagnetic material becomes paramagnetic.

Explanation

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Q 5. A charged particle moves in a uniform magnetic field of induction {tex}\overrightarrow{B}{/tex} with a velocity {tex}\overrightarrow{v}{/tex}. The change in kinetic energy in the magnetic field is zero when the velocity {tex}\overrightarrow{v}{/tex} is

A

parallel to {tex} \vec { B } {/tex}

B

perpendicular to {tex} \vec { B } {/tex}

at any angle to {tex} \vec { B } {/tex}

D

None of these

Explanation

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Q 6. An equilateral triangular current loop {tex} P Q R {/tex} carries a current I ampere. Length of each side is {tex} l {/tex} metre. A uniform magnetic field of induction {tex} \vec { B } {/tex} exists in a direction parallel to {tex} P Q {/tex} . Then the force on the side {tex} P Q {/tex} is

A

{tex} I l B {/tex}

B

{tex} \frac { I l B } { 2 } {/tex}

C

{tex} \left( \frac { I l B } { 2 } \right) \sqrt { 3 } {/tex}

Zero

Explanation

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Q 7. Two long thin wires {tex} A B C {/tex} and {tex} D E F {/tex} are arranged as shown. They carry current {tex} I {/tex} as shown. The magnitude of the magnetic field at {tex} O {/tex} is

A

Zero

B

{tex} \frac { \mu _ { 0 } I } { 4 \pi a } {/tex}

{tex} \frac { \mu _ { 0 } I } { 2 \pi a } {/tex}

D

{tex} \frac { \mu _ { 0 } I } { 2 \sqrt { 2 } \pi a } {/tex}

Explanation

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Q 8. A charged particle moves with velocity {tex} \vec { v } {/tex} in a uniform magnetic field {tex} \vec { B } . {/tex} The magnetic force experienced by the particle is

A

always zero.

B

never zero.

C

zero if {tex} \vec { B } {/tex} and {tex} \vec { v } {/tex} are perpendicular.

zero if {tex} \vec { B } {/tex} and {tex} \vec { v } {/tex} are parallel.

Explanation

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Q 9. A particle of charge {tex} - 16 \times 10 ^ { - 18 } {/tex} C moving with velocity {tex} 10 \mathrm { m } / \mathrm { s } {/tex} along the {tex} x {/tex} -axis enters a region where a magnetic field of induction {tex} B {/tex} is along the {tex} y {/tex} -axis and an electric field of magnitude {tex} 10 ^ { 4 } \mathrm { V } / \mathrm { m } {/tex} is along the negative {tex} z {/tex} -axis. If the charged particle continues moving along the {tex} x {/tex} -axis, the magnitude of {tex} B {/tex} is

{tex} 10 ^ { 3 } \mathrm { Wb } / \mathrm { m } ^ { 2 } {/tex}

B

{tex} 10 ^ { 5 } \mathrm { Wb } / \mathrm { m } ^ { 2 } {/tex}

C

{tex} 10 ^ { 16 } \mathrm { Wb } / \mathrm { m } ^ { 2 } {/tex}

D

{tex} 10 ^ { - 3 } \mathrm { Wb } / \mathrm { m } ^ { 2 } {/tex}

Explanation

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Q 10. Two concentric coils each of radius equal to 2{tex} \pi \mathrm { cm } {/tex} are placed at right angles to each other, 3{tex} \mathrm { A } {/tex} and 4{tex} \mathrm { A } {/tex} are the currents flowing in coils, respectively. The magnetic induction in {tex} \mathrm { Wb } / \mathrm { m } ^ { 2 } {/tex} at the centre of the coils will be {tex} \left( \mu _ { 0 } = 4 \pi \times 10 ^ { - 7 } \mathrm { Wb } / \mathrm { Am } \right) {/tex}

A

{tex} 12 \times 10 ^ { - 5 } {/tex}

B

{tex} 10 ^ { - 5 } {/tex}

{tex} 5 \times 10 ^ { - 5 } {/tex}

D

{tex} 7 \times 10 ^ { - 5 } {/tex}

Explanation

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Q 11. An equilateral triangular loop {tex} A C D {/tex} of side length {tex} l {/tex} carries a current {tex} i {/tex} in the direction shown in Fig. {tex} 15.41 . {/tex} The loop is kept in a uniform horizontal magnetic field {tex} \vec { B } {/tex} as shown in Fig. 15.41 , net force on the loop is

Zero

B

{tex} \frac { \sqrt { 3 } } { 2 } i B {/tex}

C

Perpendicular to paper inwards.

D

Perpendicular to paper outwards.

Explanation

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Q 12. Two particles {tex} X {/tex} and {tex} Y {/tex} having equal charges, after being accelerated through the same potential difference, enter a region of uniform magnetic field and and and and and and and and and and describe circular paths of radii {tex} R _ { 1 } {/tex} and {tex} R _ { 2 } {/tex} , respectively. The ratio of masses of {tex} X {/tex} and {tex} Y {/tex} is

A

{tex} \left( \frac { R _ { 1 } } { R _ { 2 } } \right) ^ { 1 / 2 } {/tex}

B

{tex} \frac { R _ { 2 } } { R _ { 1 } } {/tex}

{tex} \left( \frac { R _ { 1 } } { R _ { 2 } } \right) ^ { 2 } {/tex}

D

{tex} \left( \frac { R _ { 1 } } { R _ { 2 } } \right) {/tex}

Explanation

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Q 13. A current-carrying conductor is looped into a circle of radius {tex} 10 \mathrm { cm } . {/tex} The magnetic moment of the current loop becomes {tex} 0.314 \mathrm { A } / \mathrm { m } ^ { 2 } . {/tex} What is the current in the loop?

A

{tex}5 \mathrm { A } {/tex}

B

{tex}8 \mathrm A{/tex}

{tex}10 \mathrm { A } {/tex}

D

{tex}12 \mathrm { A } {/tex}

Explanation

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Q 14. Two straight long conductors {tex} A O B {/tex} and {tex} C O D {/tex} are per- pendicular to each other and carry currents {tex} i _ { 1 } {/tex} and {tex} i _ { 2 } {/tex} . The magnitude of the magnetic induction at a point {tex} P {/tex} at a distance {tex} a {/tex} from the point {tex} O {/tex} in a direction perpen- dicular to the plane {tex} A C B D {/tex} is

A

{tex} \frac { \mu _ { 0 } } { 2 \pi a } \left( i _ { 1 } + i _ { 2 } \right) {/tex}

B

{tex} \frac { \mu _ { 0 } } { 2 \pi a } \left( i _ { 1 } - i _ { 2 } \right) {/tex}

{tex} \frac { \mu _ { 0 } } { 2 \pi a } \left( i _ { 1 } ^ { 2 } + i _ { 2 } ^ { 2 } \right) ^ { 1 / 2 } {/tex}

D

{tex} \frac { \mu _ { 0 } } { 2 \pi a } \frac { i _ { 1 } i _ { 2 } } { \left( i _ { 1 } + i _ { 2 } \right) } {/tex}

Explanation

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Q 15. Shown in Fig. 15.45 is a conductor carrying a current I. The magnetic field intensity at the point {tex} O {/tex} (common centre of all the three arcs) is {tex} ( \theta \text { in radian) } {/tex}

{tex} \frac { 5 \mu _ { 0 } I \theta } { 24 \pi r } {/tex}

B

{tex} \frac { \mu _ { 0 } I \theta } { 24 \pi r } {/tex}

C

{tex} \frac { 11 \mu _ { 0 } I \theta } { 24 \pi r } {/tex}

D

Zero

Explanation



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Q 16. A particle of mass {tex} m {/tex} and charge {tex} q {/tex} is projected from origin with initial velocity {tex} [ u \hat { i } - v\hat{j}]{/tex}. Uniform electric and magnetic field exist in the region along {tex} + y {/tex} direction of magnitudes {tex} E {/tex} and {tex} B {/tex} , respectively. Then particle will definitively return to the origin if

A

{tex} \frac { v B } { 2 \pi E } {/tex} is an integer

B

{tex} \frac { \left( u ^ { 2 } + v ^ { 2 } \right) ^ { 1 / 2 } } { [ B / \pi E ] } {/tex} is an integer

{tex} \frac { v B } { \pi E } {/tex} is an integer

D

{tex} \frac { v B } { 3 \pi E } {/tex} is an integer

Explanation

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Q 17. The materials suitable for making electromagnets should have

A

High retentivity and high coercivity

Low retentivity and low coercivity

C

High retentivity and low coercivity

D

Low retentivity and high coercivity.

Explanation


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Q 18. Two parallel beams of protons and electons, carrying equal currents are fixed at a separation {tex}d{/tex}. The protons and electrons move in opposite directions. {tex} P {/tex} is a point on a line joining the beams, at a distance {tex} x {/tex} from any one beam. The magnetic field at {tex} P {/tex} is {tex} B {/tex}. If {tex} B {/tex} is plotted against {tex} x , {/tex} which of the following best represents the resulting curve

A

B

D

Explanation





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Q 19. In a current carrying long solenoid, the field produced does not depend upon

A

Number of turns per unit length

B

Current flowing

Radius of the solenoid

D

All of the above three

Explanation

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Q 20. Two concentric coils each of radius equal to {tex} 2 \pi \mathrm { cm } {/tex} are placed at right angles to each other. {tex} 3\ ampere {/tex} and {tex} 4\ ampere {/tex} are the currents flowing in each coil respectively. The magnetic induction in {tex}Weber/m^{2} {/tex} at the centre of the coils will be

{tex} 5 \times 10 ^ { - 5 } {/tex}

B

{tex} 7 \times 10 ^ { - 5 } {/tex}

C

{tex} 12 \times 10 ^ { - 5 } {/tex}

D

{tex} 10 ^ { - 5 } {/tex}

Explanation


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Q 21. A current is flowing through a thin cylindrical shell of radius {tex} R {/tex}. If energy density in the medium, due to magnetic field, at a distance {tex} r {/tex} from axis of the shell is equal to {tex} U {/tex} then which of the following graphs is correct

A

C

D

Explanation



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Q 22. A rectangular loop carrying a current {tex} i {/tex} is placed in a uniform magnetic field {tex} B {/tex}. The area enclosed by the loop is {tex} A {/tex}. If there are {tex} n {/tex} turns in the loop, the torque acting on the loop is given by

{tex} n i \vec { A } \times \vec { B } {/tex}

B

{tex} n i \vec { A } \cdot \vec { B } {/tex}

C

{tex} \frac { 1 } { n } ( \overrightarrow { i A } \times \vec { B } ) {/tex}

D

{tex} \frac { 1 } { n } ( i \vec { A } \cdot \vec { B } ) {/tex}

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Q 23. A wire carrying a current {tex} i {/tex} is placed in a uniform magnetic field in the form of the curve {tex} y = a \sin \left( \frac { \pi x } { L } \right) 0 \leq x \leq 2 L . {/tex} The force
acting on the wire is

A

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

B

{tex} i B L \pi {/tex}

{tex} 2 i B L {/tex}

D

Zero

Explanation

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Q 24. Unit of magnetic permeability is

A

Amp/ metre

B

{tex} A m p / m ^ { 2 } {/tex}

C

Henry

Henry/metre

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Q 25. If induction of magnetic field at a point is {tex} B {/tex} and energy density is {tex} U {/tex} then which of the following graphs is correct

B

C

D

Explanation