EAMCET Engineering 2008 Solved Paper

- Magnetic dipole: A Magnetic Dipole consist of two unlike poles of equivalent strength and separated by a small distance.
- Magnetic moment: It is defined as the product of pole strength and the distance between the poles of a magnet.
⇒M=m×1
where M= magnetic moment, m= pole strength and I = distance between the poles
Given L= length of wire and M= magnetic moment of straight wire If m = pole strength of magnetic wire then, the magnetic moment is ⇒M=m×L
When the wire is bent into a semicircle of radius r,
⇒L=‌ circumference of the semicircle ‌
⇒L=πr
⇒r=‌

L

π

Distance between the poles in the semicircular wire is 2r so,
⇒M′=m×2r
where M′ = magnetic moment of semicircular wire
By substituting the value of r in the above equation, we get
⇒M′=‌

2mL

π

By equation 1 and equation 2, we get
⇒M′=‌

2M

π

- Hence, option 1 is correct.