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Question: In a magnetic field of 0.05T, area of a coil changes from \(101cm^{2}\) to \(100cm^{2}\) without cha...

In a magnetic field of 0.05T, area of a coil changes from 101cm2101cm^{2} to 100cm2100cm^{2} without changing the resistance which is 2Ω. The amount of charge that flow during this period is

A

2.5×10−62.5 \times 10^{- 6}coulomb

B

2×10−62 \times 10^{- 6}coulomb

C

10−610^{- 6}coulomb

D

8×10−68 \times 10^{- 6}coulomb

Answer

2.5×10−62.5 \times 10^{- 6}coulomb

Explanation

Solution

φ=BA\varphi = BA

⇒ change in flux dφ=B.dAd\varphi = B.dA

= 0.05 6mu(101−100) 6mu10−40.05\mspace{6mu}(101 - 100)\mspace{6mu} 10^{- 4}

=5.10−6= 5.10^{- 6}Wb.

Now, charge dQ=dφR=5×10−62=2.5×10−6dQ = \frac{d\varphi}{R} = \frac{5 \times 10^{- 6}}{2} = 2.5 \times 10^{- 6}C.