If the intensity of magnetic field at a point on the axis of a current carrying coil of radius R is half of that at the centre of the coil, then the distance of that point from the centre of the coil will be
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Solution
The magnetic field at the centre of the circular loop is,
BO=μ0I2R....(1)
The magnetic field on the axis of the circular current carrying coil is,
BP=μ0IR22(R2+x2)32
According to the given information,
BP=BO2
⇒μ0IR22(R2+x2)32=μ0I4R
⇒2R3=(R2+x2)32
⇒R2×2⎛⎝23⎞⎠=R2+x2
⇒x2=R2⎛⎜
⎜⎝2⎛⎝23⎞⎠−1⎞⎟
⎟⎠
x=R√4⎛⎝13⎞⎠−1
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Hence, (D) is the correct answer.
Why this question ?
To understand the concept of magnetic field on the axis of circular current carrying coil.