Magnetics 2 Question 1

1. Find the magnetic field at point P due to a straight line segment AB of length 6cm carrying a current of 5A (See figure). (Take, μ0=4π×107NA2 )

(2019 Main, 12 April II)

(a) 2.0×105T

(b) 1.5×105T

(c) 3.0×105T

(d) 2.5×105T

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Answer:

Correct Answer: 1. (b)

Solution:

  1. The given figure can be drawn as shown below

By Biot-Savart’s law, magnetic field due to a wire segment at point P is

B=μ0I4πd(sinθ1+sinθ2)

Here,

θ1=θ2=θ

Then,

B=μ0I4πd×2sinθ

From given data,

I=5A,μ=4π×107NA2d=5232=16=4cmsinθ=35

On substituting these values in Eq. (i), we get

B=μ0I4πd×2sinθ=4π×107×54π×4×102×2×35=5×2×34×5×105=1.5×105T



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