NEET Practice Questions (MCQs) with Answers & Solutions

According to the provided text, 'Thus, Gauss’s law for magnetism is: The net magnetic flux through any closed surface is zero.' This is the core statement of the law.

The text states: 'The difference between the Gauss’s law of magnetism and that for electrostatics is a reflection of the fact that isolated magnetic poles (also called monopoles) are not known to exist.' And in 'MOVING_CHARGES_AND_MAGNETISM' chapter, it's mentioned 'These lines called magnetic field lines form closed loops. This is unlike the electrostatic field lines which originate from positive charges and end at negative charges.' The absence of monopoles means there are no sources or sinks for magnetic field lines, hence they must form closed loops.

The text states: 'Ampere’s law is to Biot-Savart law, what Gauss’s law is to Coulomb’s law. Both, Ampere’s and Gauss’s law relate a physical quantity on the periphery or boundary (magnetic or electric field) to another physical quantity, namely, the source, in the interior (current or charge).'

The text clearly states: 'There are no sources or sinks of B; the simplest magnetic element is a dipole or a current loop.'

From the 'MOVING_CHARGES_AND_MAGNETISM' section, it's mentioned: 'These lines called magnetic field lines form closed loops. This is unlike the electrostatic field lines which originate from positive charges and end at negative charges.'

The equation $\oint \vec{B} \cdot d\vec{A} = 0$ means that the net magnetic flux passing through any closed surface is zero. This is a direct consequence of the non-existence of magnetic monopoles, implying that magnetic field lines have no starting or ending points (sources or sinks) within a closed surface, and thus must form closed loops, entering and leaving the surface in equal amounts.

Gauss's Law for Magnetism states, 'The net magnetic flux through any closed surface is zero.' This holds true irrespective of what is enclosed by the surface (assuming no magnetic monopoles). It's distinct from Ampere's Law, which relates the line integral of B to the enclosed current.

The text states: 'Ampere’s circuital law is not new in content from Biot-Savart law... Ampere’s law is to Biot-Savart law, what Gauss’s law is to Coulomb’s law.'

The text highlights this key difference: 'The difference between the Gauss’s law of magnetism and that for electrostatics is a reflection of the fact that isolated magnetic poles (also called monopoles) are not known to exist... These lines called magnetic field lines form closed loops. This is unlike the electrostatic field lines which originate from positive charges and end at negative charges.'

In the absence of an electric field, electrons move randomly. If we consider all the electrons, their average velocity will be zero since their directions are random. (NCERT, Section 3.5, page 85)