Question

A magnetic field $$\overrightarrow B = {B_0}\hat j,$$   exists in the region $$a < x < 2a,$$   and $$\overrightarrow B = - {B_0}\hat j,$$   in the region $$2a < x < 3a,$$   where $${B_0}$$ is a positive constant. A positive point charge moving with a velocity $$v = {v_0}\hat i,$$  where $${v_0}$$ is a positive constant, enters the magnetic field at $$x = a.$$  The trajectory of the charge in this region can be like
Magnetic Effect of Current mcq question image

A. Magnetic Effect of Current mcq option image  
B. Magnetic Effect of Current mcq option image
C. Magnetic Effect of Current mcq option image
D. Magnetic Effect of Current mcq option image
Answer :   Magnetic Effect of Current mcq option image
Solution :
Use the vector form of $$B$$ and $$v$$ in the formulae $$\overrightarrow F = q\left( {\overrightarrow v \times \overrightarrow B } \right)$$    to get the instantaneous direction of force at $$x = a$$  and $$x = 2a.$$

Releted MCQ Question on
Electrostatics and Magnetism >> Magnetic Effect of Current

Releted Question 1

A conducting circular loop of radius $$r$$ carries a constant current $$i.$$ It is placed in a uniform magnetic field $${{\vec B}_0}$$ such that $${{\vec B}_0}$$ is perpendicular to the plane of the loop. The magnetic force acting on the loop is

A. $$ir\,{B_0}$$
B. $$2\pi \,ir\,{B_0}$$
C. zero
D. $$\pi \,ir\,{B_0}$$
Releted Question 2

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

A. proportional to $$2\left( {{{180}^ \circ } - \theta } \right)$$
B. inversely proportional to $$r$$
C. zero, only if $$\theta = {180^ \circ }$$
D. zero for all values of $$\theta $$
Releted Question 3

A proton, a deuteron and an $$\alpha - $$ particle having the same kinetic energy are moving in circular trajectories in a constant magnetic field. If $${r_p},{r_d},$$  and $${r_\alpha }$$ denote respectively the radii of the trajectories of these particles, then

A. $${r_\alpha } = {r_p} < {r_d}$$
B. $${r_\alpha } > {r_d} > {r_p}$$
C. $${r_\alpha } = {r_d} > {r_p}$$
D. $${r_p} = {r_d} = {r_\alpha }$$
Releted Question 4

A circular loop of radius $$R,$$ carrying current $$I,$$ lies in $$x - y$$  plane with its centre at origin. The total magnetic flux through $$x - y$$  plane is

A. directly proportional to $$I$$
B. directly proportional to $$R$$
C. inversely proportional to $$R$$
D. zero

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