Many of the diagrams given in the figure show magnetic field lines (thick lines in the figure) wrongly. Point out what is wrong with them. Some of them may describe electrostatic field lines correctly. Point out which ones.

Vedclass pdf generator app on play store
Vedclass iOS app on app store
(N/A) Wrong. Magnetic field lines can never emanate from a point,as shown in the figure. Over any closed surface,the net flux of $B$ must always be zero,i.e.,pictorially as many field lines should seem to enter the surface as the number of lines leaving it. The field lines shown,in fact,represent the electric field of a long positively charged wire. The correct magnetic field lines are circling the straight conductor.
$(b)$ Wrong. Magnetic field lines (like electric field lines) can never cross each other,because otherwise the direction of the field at the point of intersection is ambiguous. There is a further error in the figure. Magnetostatic field lines can never form closed loops around empty space. $A$ closed loop of a static magnetic field line must enclose a region across which a current is passing. By contrast,electrostatic field lines can never form closed loops,neither in empty space,nor when the loop encloses charges.
$(c)$ Right. Magnetic lines are completely confined within a toroid. Nothing is wrong here in field lines forming closed loops,since each loop encloses a region across which a current passes. Note,for clarity of the figure,only a few field lines within the toroid have been shown. Actually,the entire region enclosed by the windings contains a magnetic field.
$(d)$ Wrong. Field lines due to a solenoid at its ends and outside cannot be so completely straight and confined; such a thing violates Ampere's law. The lines should curve out at both ends and meet eventually to form closed loops.
$(e)$ Right. These are field lines outside and inside a bar magnet. Note carefully the direction of field lines inside. Not all field lines emanate out of a north pole (or converge into a south pole). Around both the $N$-pole and the $S$-pole,the net flux of the field is zero.
$(f)$ Wrong. These field lines cannot possibly represent a magnetic field. Look at the upper region. All the field lines seem to emanate out of the shaded plate. The net flux through a surface surrounding the shaded plate is not zero. This is impossible for a magnetic field. The given field lines,in fact,show the electrostatic field lines around a positively charged upper plate and a negatively charged lower plate. The difference between Figure $(e)$ and $(f)$ should be carefully grasped.
$(g)$ Wrong. Magnetic field lines between two pole pieces cannot be precisely straight at the ends. Some fringing of lines is inevitable. Otherwise,Ampere's law is violated. This is also true for electric field lines.

Explore More

Similar Questions

Two short magnets of magnetic moment $1000 \, A m^2$ are placed as shown at the corners of a square of side $10 \, cm$. The net magnetic induction at $P$ is....$T$

Match List-$I$ with List-$II$.
List-$I$List-$II$
$(A)$ Magnetic induction$(I)$ Ampere meter$^2$
$(B)$ Magnetic intensity$(II)$ Weber
$(C)$ Magnetic flux$(III)$ Gauss
$(D)$ Magnetic moment$(IV)$ Ampere meter

Choose the correct answer from the options given below:

For a ferromagnetic material,the relative permeability $(\mu_r)$ versus magnetic intensity $(H)$ has the following shape:

Magnetostatic screening or shielding can be created by

Two magnets of equal mass are joined at right angles to each other as shown. Magnet $1$ has a magnetic moment $3$ times that of magnet $2$. This arrangement is pivoted so that it is free to rotate in the horizontal plane. In equilibrium,what angle will magnet $1$ subtend with the magnetic meridian?

Difficult
View Solution

Vedclass Products

For Students

Vedclass Test Series

Mock tests in real JEE/NEET style with performance analysis. 5-day free trial.

Start Free Trial
For Teachers

Exam Paper Generator

Generate Set A/B/C/D exam papers from 7.5L+ questions in 2 minutes. 3 chapters free.

Try Free
For Institutes

Online Exam Module

Live online exams with unlimited students, 360° analytics & white-label branding.

See Demo