Question
Explain : Bar magnet as an equivalent solenoid.
✓
Answer
→Every current loop acts as a magnetic dipole. (In the previous chapter we have explained). We mentioned in Ampere's hypothesis that all magnetic phenomena can be explained in terms of circulating current.
→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.
→Cutting a bar magnet in half is like cutting a solenoid. We get two smaller solenoids with weaker magnetic properties. The field lines remain continuous, emerging from one face of the solenoid and entering in to the other face.
→One can test this analogy by moving a small compass needle in the neighbourhood of a bar magnet and a current carring finite solenoid and nothing that the deflections of the needle are similar in both cases.
→To make this analogy more firm we calculate the axial field of a finite solenoid depicted in fig. We shall demonstrate that at large distance this axial field resembles that of a bar magnet.
→ Magnetic field on axis of solenoid is
$B =\frac{\mu_0}{4 \pi} \cdot \frac{2 m}{r^3}$
→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 a similar magnetic field. The magnetic moment of a bar magnet and a solenoid produce similar magnetic field. The magnetic moment of a bar magnet is thus, equal to magnetic moment of an equivalent solenoid that produces the same magnetic field.
Need a full question paper?
Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.
Explore more
Similar questions
A square coil of edge l and with n turns carries a current i. It is kept on a smooth horizontal plate. A uniform magnetic field B exists parallel to an edge. The total mass of the coil is M. What should be the minimum value of B for which the coil will start tipping over?
Does the temperature of a body depend on the frame from which it is observed?
A 12 pF capacitor is connected to a 50 V battery. How much electrostatic energy is stored in the capacitor? If another capacitor of 6 pF is connected in series with it with the same battery connected across the combination, find the charge stored and potential difference across each capacitor.
Define the terms half-life period and decay constant of a radioactive substance. Write their S.I.units. Establish the relationship between the two.
A person has near point at 100cm. What power of lens is needed to read at 20cm if he/ she uses.
- Contact lens,
- Spectacles having glasses 2.0cm separated from the eyes?
An electric bulb is designed to operate at 12 volts DC. If this bulb is connected to an AC source and gives normal brightness, what would be the peak voltage of the source?
A long charged cylinder of linear charged density λ is surrounded by a hollow co-axial conducting cylinder. What is the electric field in the space between the two cylinders?
Explain how radioactive nuclei can emit $\beta-$particles even though atomic nuclei do not contain these particles? Hence explain why the mass number of radioactive nuclide does not change during $\beta-$decay?
→A magnetic flux of 8 × 10-4 weber is linked with each turn of a 200-turn coil when there is an electric current of 4A in it. Calculate the self-inductance of the coil.
Calculate the number of photons emitted per second by a 10W sodium vapour lamp. Assume that 60% of the consumed energy is converted into light. Wavelength of sodium light = 590nm.