Moving Charges And Magnetism
The magnetic effect of current was first discovered by H.C. Oersted. He observed that the flow of charges in a conductor produces magnetic effect around it.
RightHand Thumb Rule
According to this rule, if we grasp the currentcarrying wire in our right hand such that our thumb points in the direction of current, then the direction in which our fingers encircle the wire will tell the direction of the magnetic field lines around the wire.
The Biot–Savart Law
 According to this law, the magnetic field is proportional to the current and element length and inversely proportional to the square of the distance.

$dB=\frac{Idl\mathrm{sin}\theta}{{r}^{2}}$
Magnetic field due to a currentcarrying circular coil

At the centre, it is calculated to be equal to B.

$B=\frac{{\mu}_{0}nI}{r}$

Here,
n = Number of turns in the coil
I = …

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