23 re along the radius Two concentric coils of 10 turns each are situated in the same plane. Their radii are 2cm and 4cm and they carry respectively 0.2 and 0.3A current in opposite directions. The magnetic field (in Wb/m2) at the centre is 1) (3) 40 2) 23 ("%80) 3) (780)4 3 4) (252) H.
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Answer:
Correct option is D)
The magnetic field due to the circular coil at the center is given by,
B
=
4π
μ
0
r
2πni
The magnetic field due to the first circular coil is given by,
B
1
=
4π
μ
0
r
1
2πni
1
The magnetic field due to the second circular coil is given by,
B
2
=−
4π
μ
0
r
2
2πni
2
The resultant magnetic field is given by,
B=B
1
+B
2
B=
4π
μ
0
r
1
2πni
1
−
4π
μ
0
r
2
2πni
2
B=
2
μ
0
[
r
1
ni
1
−
r
2
ni
2
]
B=
2
μ
0
[
0.20
10×0.2
−
0.40
10×40
]
B=0
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