Magnetic Effects of Current and Magnetism MCQs for NEET — Physics Questions with Answers

The NCERT text explicitly states: 'The magnetic field lines do not intersect, for if they did, the direction of the magnetic field would not be unique at the point of intersection.' Options 1, 2, and 4 are all stated as properties of magnetic field lines.

The NCERT text provides: 'In particular, we can write down the equatorial field ($B_E$) of a bar magnet at a distance r, for $r >> l$, where l is the size of the magnet: $B_E = -\frac{\mu_0}{4\pi} \frac{m}{r^3}$ (5.4).' This matches option 2.

The NCERT text states: 'Comparison of Eqs. (5.1), (5.2) and (5.3) with the corresponding equations for electric dipole (Chapter 1), suggests that magnetic field at large distances due to a bar magnet of magnetic moment m can be obtained from the equation for electric field due to an electric dipole of dipole moment p, by making the following replacements: $\vec{E} \to \vec{B}$, $\vec{p} \to \vec{m}$, $\frac{1}{4\pi\epsilon_0} \to \frac{\mu_0}{4\pi}$'. This set of replacements is correctly reflected in option 3.

The NCERT text says: 'In Fig. 4.15(a), it is clear from the circular loops that the field between two neighbouring turns vanishes.' This directly supports option 2.

The NCERT text states: 'The torque on the needle is [see Eq. (4.23)], $\vec{\tau} = \vec{m} \times \vec{B}$ (5.2). In magnitude $\tau = mB \sin\theta$. Here $\tau$ is restoring torque and $\theta$ is the angle between $m$ and $B$.' Since a solenoid acts as a bar magnet, this applies to the equivalent solenoid as well. Therefore, $\theta$ is the angle between the magnetic moment ($m$) and the magnetic field ($B$). This aligns with option 3.

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.'