Many of the diagrams given in Fig 5.7 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.

Explanation

(a) The field lines shown in figure (a), do not represent magnetic field lines because for a current carrying straight long wire, the magnetic field lines are circular with the centres on the wire. They can not be radial as shown in the figure.
Here the field lines resemble with those of line of positive charges.
(Note : In figure (a) if we imagine a closed surface around the wire then `oint overset(to) (B) . overset(to) (d) a ne 0`
which is against Gauss.s law for magnetism. Hence, these are not magnetic field lines).
(b) (i) Electric field lines never intersect and magnetic field lines also never intersect. Hence, crossed lines shown in figure (b) are neither electric nor magnetic.
(ii) The circular field lines shown in figure (b) can not be electrostatic field lines because they never form closed loops. They can not be even magnetic field lines because they do not enclose any current.
(c) The field lines shown in figure (c) are magnetic field lines in the toroidal region when steady current is passed through the windings of a toroid. As they form closed loops, they can not be electrostatic field lines.
(d) In figure (d), the pattern of magnetic field lines inside the current carrying solenoid is wrong because they are shown straight near the ends and outside the solenoid such straight field lines do not form closed loops and so they are wrong. They can not represent even electric field lines because there are no charges inside the solenoid.
(e) Field lines shown in figure (e) represent magnetic field lines of a bar magnet. But they do not show electric field lines because they form closed loops.
(f) Field lines shown in figure (f) do not represent magnetic field lines because net magnetic flux passing through closed surfaces chosen around two horizontal plates is not zero which is against Gauss.s law for magnetism.
Here field lines represent electrostatic field lines around positively charged upper plate and negatively charged lower plate.
(g) Field lines shown in figure (g) do not show magnetic field lines because all of them are perfect straight lines. In reality, magnetic field lines near the edges of poles are always curved. This phenomenon is called "fringing" of field which is not seen in the diagram. This is also true for electric field.