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

The NCERT text states: 'The resemblance of magnetic field lines for a bar magnet and a solenoid suggest that a bar magnet may be thought of as a large number of circulating currents in analogy with a solenoid.' This directly supports option 3. Option 1 is incorrect as magnetic field lines are continuous closed loops, unlike electric dipoles. Option 2 is incorrect because magnetic monopoles do not exist. Option 4 is incorrect as the field inside a long solenoid is uniform.

The NCERT text states: 'Cutting a bar magnet in half is like cutting a solenoid. We get two smaller solenoids with weaker magnetic properties.' This directly supports option 2. Option 1 is incorrect because magnetic monopoles do not exist. Options 3 and 4 are incorrect because magnetic field lines remain continuous.

The NCERT text states: 'The magnitude of the field at point P due to the solenoid is $B = \frac{\mu_0}{4\pi} \frac{2m}{r^3}$ (5.1). This is also the far axial magnetic field of a bar magnet which one may obtain experimentally. Thus, a bar magnet and a solenoid produce similar magnetic fields.' This confirms that the given expression represents the far axial field of a finite solenoid.

The NCERT text states: 'The magnetic field lines of a magnet (or a solenoid) form continuous closed loops.' This is a key property of magnetic field lines. Option 2 describes electric field lines, not magnetic. Option 4 is incorrect as magnetic field lines never intersect.

The NCERT text says: 'One can test this analogy by moving a small compass needle in the neighbourhood of a bar magnet and a current-carrying finite solenoid and noting that the deflections of the needle are similar in both cases.' This directly supports option 3.

The NCERT text states: 'The magnetic moment of a bar magnet is thus equal to the magnetic moment of an equivalent solenoid that produces the same magnetic field.' This directly matches option 4.

The NCERT text shows 'FIGURE 5.2 The field lines of (a) a bar magnet, (b) a current-carrying finite solenoid and (c) electric dipole. At large distances, the field lines are very similar.' It also mentions 'For comparison refer to the Chapter 1, Figure 1.14(d). Electric field lines of an electric dipole are also displayed in Fig. 5.2(c).' This indicates similarity in field lines at large distances.

The NCERT text states: 'We mentioned Ampere’s hypothesis that all magnetic phenomena can be explained in terms of circulating currents.' This directly supports option 3.

While not explicitly stated in the provided text for a bar magnet, the property of magnetic field lines emerging from one face and entering another is stated for a solenoid: 'The field lines remain continuous, emerging from one face of the solenoid and entering into the other face.' By analogy and general magnetic principles (which candidates for NEET are expected to know), magnetic field lines emerge from the North pole and enter the South pole outside a magnet. The provided context about iron filings also implies this pattern.

The NCERT text states: 'In Fig. 4.15(b), we see that the field at the interior mid-point P is uniform, strong and along the axis of the solenoid.' This directly supports option 2.