1.

A circular coil of radius 8cm, 400 turns and resistance 2Omega is placed with its plane perpendicular to the horizantal component of the earth's magnetic fiedl. It is rotated about its vertical diameter through 180^(@) in 0.30 s. Horizontal component of earth magnitude of current induced in the coil is approximately

Answer»

`4xx10^(-2)A`
`8xx10^(-4)A`
`8xx10^(-2)A`
`1.92xx10^(-3)A`

Solution :Initial flux through the coil
`phi_(i)=BAcos theta`
`=3xx10^(-5)xxpixx(8xx10^(-2))xxcos 0^(@)`
`=192pixx10^(-9)Wb`
FINAL flux after the rotation
`phi_(F)=3xx10^(-5)xxpi(8xx10^(-2))^(2)cos 180^(@)`
`=-192pixx10Wb`
`:.` TEH magnitude of induced emf is
`epsi=N|(dphi|)/(dt)=(N|phi_(f)phi_(i)|)/(dt)`
`=(400xxx(384pxx10^(-9)))/(0.30)=1.6xx10^(-3)V`
Current `I=(epsi)/(R)=(1.6xx10^(-3))/(2)=8xx10^(-4)A`


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