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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
{tex} 2 \pi \times 10 ^ { - 5 } {/tex} Tesla
{tex} 4 \pi \times 10 ^ { - 2 } {/tex} Gauss
{tex} 2 \pi \times 10 ^ { - 5 } {/tex} Gauss
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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
Magnetic meridian
Magnetic axis
Magnetic line
Magnetic equator
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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}
{tex} \frac { \mu _ { 0 } I} { 2 \pi r } ( 1 + \pi ) {/tex}
{tex} \frac { \mu _ { 0 } I } { \pi r } ( 1 + \pi ) {/tex}
{tex} \frac { \mu _ { 0 } I } { r } ( 1 + \pi ) {/tex}
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Q 4. Curie temperature is the temperature above which
a paramagnetic material becomes diamagnetic.
a ferromagnetic material becomes diamagnetic.
a paramagnetic material becomes ferromagnetic.
a ferromagnetic material becomes paramagnetic.
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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
parallel to {tex} \vec { B } {/tex}
perpendicular to {tex} \vec { B } {/tex}
at any angle to {tex} \vec { B } {/tex}
None of these
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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
{tex} I l B {/tex}
{tex} \frac { I l B } { 2 } {/tex}
{tex} \left( \frac { I l B } { 2 } \right) \sqrt { 3 } {/tex}
Zero
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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
Zero
{tex} \frac { \mu _ { 0 } I } { 4 \pi a } {/tex}
{tex} \frac { \mu _ { 0 } I } { 2 \pi a } {/tex}
{tex} \frac { \mu _ { 0 } I } { 2 \sqrt { 2 } \pi a } {/tex}
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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
always zero.
never zero.
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.
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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}
{tex} 10 ^ { 5 } \mathrm { Wb } / \mathrm { m } ^ { 2 } {/tex}
{tex} 10 ^ { 16 } \mathrm { Wb } / \mathrm { m } ^ { 2 } {/tex}
{tex} 10 ^ { - 3 } \mathrm { Wb } / \mathrm { m } ^ { 2 } {/tex}
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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}
{tex} 12 \times 10 ^ { - 5 } {/tex}
{tex} 10 ^ { - 5 } {/tex}
{tex} 5 \times 10 ^ { - 5 } {/tex}
{tex} 7 \times 10 ^ { - 5 } {/tex}
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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
{tex} \frac { \sqrt { 3 } } { 2 } i B {/tex}
Perpendicular to paper inwards.
Perpendicular to paper outwards.
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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
{tex} \left( \frac { R _ { 1 } } { R _ { 2 } } \right) ^ { 1 / 2 } {/tex}
{tex} \frac { R _ { 2 } } { R _ { 1 } } {/tex}
{tex} \left( \frac { R _ { 1 } } { R _ { 2 } } \right) ^ { 2 } {/tex}
{tex} \left( \frac { R _ { 1 } } { R _ { 2 } } \right) {/tex}
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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?
{tex}5 \mathrm { A } {/tex}
{tex}8 \mathrm A{/tex}
{tex}10 \mathrm { A } {/tex}
{tex}12 \mathrm { A } {/tex}
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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
{tex} \frac { \mu _ { 0 } } { 2 \pi a } \left( i _ { 1 } + i _ { 2 } \right) {/tex}
{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}
{tex} \frac { \mu _ { 0 } } { 2 \pi a } \frac { i _ { 1 } i _ { 2 } } { \left( i _ { 1 } + i _ { 2 } \right) } {/tex}
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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}
{tex} \frac { \mu _ { 0 } I \theta } { 24 \pi r } {/tex}
{tex} \frac { 11 \mu _ { 0 } I \theta } { 24 \pi r } {/tex}
Zero
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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
{tex} \frac { v B } { 2 \pi E } {/tex} is an integer
{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
{tex} \frac { v B } { 3 \pi E } {/tex} is an integer
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Q 17. The materials suitable for making electromagnets should have
High retentivity and high coercivity
Low retentivity and low coercivity
High retentivity and low coercivity
Low retentivity and high coercivity.
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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
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Q 19. In a current carrying long solenoid, the field produced does not depend upon
Number of turns per unit length
Current flowing
Radius of the solenoid
All of the above three
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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}
{tex} 7 \times 10 ^ { - 5 } {/tex}
{tex} 12 \times 10 ^ { - 5 } {/tex}
{tex} 10 ^ { - 5 } {/tex}
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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
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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}
{tex} n i \vec { A } \cdot \vec { B } {/tex}
{tex} \frac { 1 } { n } ( \overrightarrow { i A } \times \vec { B } ) {/tex}
{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
{tex} \frac { i B L } { \pi } {/tex}
{tex} i B L \pi {/tex}
{tex} 2 i B L {/tex}
Zero
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Q 24. Unit of magnetic permeability is
Amp/ metre
{tex} A m p / m ^ { 2 } {/tex}
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
