Force Due to Magnetic Field-Assignment

FORCE DUE TO MAGNETIC FIELDASSIGNMENT

S H I VA R A M P R A S A D

SINGLE OPTION CORRECT

1.A particle of charge q and mass m is projected with a velocity v0 towards a circular region having uniform magnetic field B perpen-dicular and into the plane of paper from point P as shown in the figure. R is the radius and O is the centre of the circular region. If the line OP makes an angle with the direction of v0 then the value of v0 so that particle passes through O is

(A) (B) (C) (D)

2.A very long current carrying wire is placed along z-axis having current of magnitude i1 towards negative z-axis. A semicircular wire of radius R and having current i2 is placed in x-y plane, such that line joining two end points of the semicircular wire passes through long wire as shown in figure. Nearest distance of semicircular wire from long wire is R. Net magnetic force on semicircular wire will be

(A) (B) (C) zero (D)

3.A particle having mass m, charge q is projected with velocity v0 along y-axis in a region of uniform magnetic field B0 which is out-ward and perpendicular to the plane of the paper as shown in the figure. The particle is continuously subjected to a frictional force which

varies with velocity as , where is a constant. Consequently the particle moves on a spiral path till it comes to rest at point P. The

x-coordinate of point P is (Take = 10-3 kg/s, q = 10-3 C, B0 = 1T, v0 = 1 m/s, m = 20gm)

(A) 10 m (B) 4 m (C) 6 m (D) 8 m

4.A direct current flowing through the winding of a long cylindrical solenoid of radius R produces in it a uniform magnetic field of induction B. An electron flies into the solenoid along the radius between its turns (at right angles to the solenoid axis) at a velocity v as shown in figure. After a certain time, the electron deflected by the magnetic field leaves the solenoid. Then the time t during which the electron moves in the solenoid is

(A) (B) (C) (D)

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5.A uniform current carrying ring of mass m and radius R is connected by a massless string as shown. A uniform magnetic field B0 exist in the region to keep the ring in horizontal position, then the current in the ring is ( = length of string)

(A) (B) (C) (D)

6.There is a long cylindrical pipe wire of external radius r and internal radius R carrying current I along its length. The variation of magnetic field with distance from the axis of the wire can be represented by the

7.A square loop of side 2 cm carrying current I0 is placed in x-y plane in a magnetic field T. Find the unit vector

along the axis about which it will start rotating

(A) (B) (C) (D)

8.Two straight long conductors AOB and COD are perpendicular to each other and carry currents i1 and i2. The magnitude of the magnetic induction at a point P at a distance a from the point O in a direction perpendicular to the plane ACBD is

(A) (B) (C) (D)

MORE THAN ONE OPTION CORRECT

9.A charged particle enters a region which offers some resistance against its motion and a uniform magnetic field exists in the region. The particle traces a spiral path as shown. Then :

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(A) angular velocity of particle remains constant (B) speed of particle decreases continuously

(C) total mechanical energy of the particle remains conserved

(D) net force on the particle is always perpendicular to its direction of motion

10. A coil in the shape of an equilateral triangle of side 0.02 m is suspended from vertex such that it is hanging in a ver-

tical plane between the pole-pieces of a permanent magnet producing a horizontal magnetic field of . Current in loop is

0.1 A. Then

(A) magnetic moment of the loop is

(B) magnetic moment of the loop is

(C) couple acting on the coil is

(D) couple acting on the coil is

11. Two circular coils of radii 5 cm and 10 cm carry equal currents of 2A. The coils have 50 and 100 turns respectively and are placed in such a way that their planes as well as their centres coincide. Magnitude of magnetic field at the common centre of coils is

(A) T if current in the coil are in same sense

(B) T if current in the coil are in opposite sense

(C) zero if currents in the coils are in opposite sense

(D) T if current in the coil are in opposite sense

12. A narrow beam of singly charged carbon ions, moving at a constant velocity of m/s is sent perpendicularly

in a rectangular region having uniform magnetic field B = 0.5T. It is found that two beams emerge from the field in the backward

direction, the separations from the incident beam 3cm and 3.5 cm. If mass of an ion = kg where A is the mass num-

ber than isotopes present in beam are

(A) (B) (C) (D)

REASONING TYPE

13. Statement-1 : The mathematical statement of ampere’s law is true when variable electric field is not pre-

sent in the medium.

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Statement-2 : A variable electric field produces magnetic field

14. Statement-1 : A charged particle moves perpendicular to a uniform magnetic field then its momentum remains con-stant

Statement-2 : Magnetic force acts perpendicular to the velocity of the particle

15. Statement-1 : A beam of electron can pass undeflected through a region of and .

Statement-2 : Force on moving charge particle due to magnetic field may be zero

16. Statement-1 ; The magnetic field at the centre of the circular coil in the following figure is zero

Statement-2 : Since I1 = I2, therefore the magnetic field due to one part balances that due to the other part of the circle.

MATRIX MATCHING

17. Match the following

Column – IColumn – I Column –IIColumn –II

A) A change particle is moving in uniform electric and magnetic field in gravity free space

p) Velocity of the particle may be constant

B) A charge particle is moving in uniform electric magnetic field and gravitational field

q) Path of particle may be straight line

C) A charge particle is moving in uniform magnetic and gravitational field (where electric field is zero)

r) Path of particle may be circular

D) A charge particle is moving in only uniform electric field

s) Path of particle may be helical

18. A square loop is placed near a long straight current carrying wire as shown. Match the following table


A) If current is increased p) Induced current in loop is clockwiseB) If current is decreased q) Induced current in loop is anticlockwise

C) If loop is moved away from the wire r) Wire will attract the loop

D) If loop is moved towards the wire s) Wire will repel the loop

19. A circular current carrying loop of 100 turns and radius 10 cm is placed in x-y plane as shown. A uniform mag-

netic field tesla is present in the region. If current in the loop is 5A, then match the following

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5π


A) Magnitude and direction of magnetic moment (in A-m) of the loop

p) zero

B) Magnitude and direction of torque (in N-m) on the loop

q)

C) Magnitude and direction of net force (in N) on the current loop

r) along positive z-axis

D) Direction of magnetic field of loop at the centre s) along negative y-axis

20. Match the Column-I with Column –II


A) Magnetic flux density due to a current carrying circular coil

p) Zero

B) Magnetic flux density at a point on a current carrying thin wire

q) Maximum of zero at the centre

C) Electric field strength due to an uniformly charged ring

r) Continuously decreases as we move away from the centre along the axis

D) Electric field due to an uniformly charged ring s) Continuously increases as we move away from the centre upto a definite distance along the axis.

21. A square loop of side a and carrying current i as shown in the figure is placed in gravity free space having magnetic

field . Now match following :


A) Torque on loop p) is zeroB) Net force on loop q) is along x-axis

C) Potential energy of loop r) is along negative z-axis

D) Magnetic moment of loop s) has maximum magnitudes

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22. A charged particle passes through a region that could have electric field only or magnetic field only or both electric and magnetic fields or none of the fields.


A) Kinetic energy of the particle remains constant p) Under special conditions, this is possible when both electric and magnetic fields are present

B) Acceleration of the particle is zero q) The region has electric field only

C) Kinetic energy of the particle changes and it also suffers deflection

r) The region has magnetic field only

D) Kinetic energy of he particle changes but it suffers no deflection

s) The region contains no field

PASSAGE

The magnetic force on a moving charge is given by . Further when a charge particle moves in uniform magnetic

field such that its velocity is perpendicular to the magnetic field then its path is circular.

A particle with charge 2.4 C and kg is initially traveling in the +y direction with a speed m/s. It then

enters a region containing a uniform magnetic field that is directed into, and perpendicular to, the edge. The magnitude of field is 0.360 T. The region extends a distance of 30 cm along the initial direction of travel; 75 cm from the point of entry into the mag-netic field region there is a wall. The length of the field free region is thus 45 cm. When the charged particle enters the magnetic field, it follows a curved path whose radius of curvature is r. It then leaves the magnetic field after time t1, having been deflected a distance . The particle then travels in the field-free region and strikes the wall after undergoing a total deflection .

23. The radius r of the curved part of the path is

(A) 0.25 m (B) 0.5 m (C) 1 m (D) 2 m

24. The time the particle spends in the magnetic field is

(A) 0.6 (B) 1.2 (C) 1.8 (D) 2.4

25. The horizontal deflection at the point of exit from the field is

(A) 0.01 m (B) 0.02 m (C) 0.2 m (D) 0.1 m

26. The total horizontal deflection is

(A) 0.1 m (B) 0.44 m (C) 0.34 m (D) 0.14 m

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1 D 2 A 3 B 4 A 5 A 6 A 7 A8 C 9 C 10 B, C 11 A, B, C, D 12 B, D 13 B 14 D15 A 16 B 17 A 18 D 19 A 20 B 21 D22 A 23. A-q, s; B-p, s; C-q, s; D-p, sA-q, s; B-p, s; C-q, s; D-p, sA-q, s; B-p, s; C-q, s; D-p, s 24. A-q, B-t, C- t, D-pA-q, B-t, C- t, D-pA-q, B-t, C- t, D-p 25. A-r, B-p, C-q, D-sA-r, B-p, C-q, D-sA-r, B-p, C-q, D-s

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Force Due to Magnetic Field-Assignment