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Question: If a coil of 40 turns and area 4 cm2 is suddenly removed from a magnetic field, it is observed that ...

If a coil of 40 turns and area 4 cm2 is suddenly removed from a magnetic field, it is observed that a charge of 2 × 10-4 C flows into the coil, if resistance of the coil is 80 Ω\Omega , the magnetic flux density in Wb m -2 is

A

0.5

B

1

C

1.5

D

2

Answer

1

Explanation

Solution

Here , N = 40, A=4 cm2=4×10−4 m2\mathrm { A } = 4 \mathrm {~cm} ^ { 2 } = 4 \times 10 ^ { - 4 } \mathrm {~m} ^ { 2 }

As

⇒B=q×RNA=2×10−4×8040×4×10−4=1Wbm−2\Rightarrow \mathrm { B } = \frac { \mathrm { q } \times \mathrm { R } } { \mathrm { NA } } = \frac { 2 \times 10 ^ { - 4 } \times 80 } { 40 \times 4 \times 10 ^ { - 4 } } = 1 \mathrm { Wbm } ^ { - 2 }