Question:

A battery is connected between two points A and B on the circumference of a uniform conducting ring of radius r andresistance R. One of the arcs AB of the ring subtends an angle $\theta$ at the centre. The value of the magnetic induction at the centre due to the current in the ring is

Updated On: Jun 14, 2022
  • proportional to $(180^\circ-\theta)$
  • inversely proportional to r
  • zero, only if $(\theta=180^\circ)$
  • zero for all values of $\theta$
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The Correct Option is D

Solution and Explanation

For a current flowing into a circular arc, the magnetic induction at the centre is
$B=\Bigg(\frac{\mu_0 i}{4\pi r}\Bigg)\theta$
$or \, \, \, \, \, \, \, \, \, B ? i \theta$
In the given problem, the total current is divided into two arcs
$\hspace15mm i ? \frac{1}{resistance of arc} ?\frac{1}{length of arc }$
$\hspace15mm ?\frac{1}{angle subtended at centre(\theta)}$
$or \, \, \, \, \, \, \, \, \, \, i\theta= constant$
i.e. magnetic field at centre due to arc AB is equal and opposite to the magnetic field at centre due to arc ACB. Or the net magnetic field at centre is zero.
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Moving charges generate an electric field and the rate of flow of charge is known as current. This is the basic concept in Electrostatics. Another important concept related to moving electric charges is the magnetic effect of current. Magnetism is caused by the current.

Magnetism:

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  • And Magnetism is a property that is displayed by Magnets and produced by moving charges, which results in objects being attracted or pushed away.

Magnetic Field:

Region in space around a magnet where the Magnet has its Magnetic effect is called the Magnetic field of the Magnet. Let us suppose that there is a point charge q (moving with a velocity v and, located at r at a given time t) in presence of both the electric field E (r) and the magnetic field B (r). The force on an electric charge q due to both of them can be written as,

F = q [ E (r) + v × B (r)] ≡ EElectric +Fmagnetic 

This force was based on the extensive experiments of Ampere and others. It is called the Lorentz force.