A circular coil of radius 6 cm and 20 turns rotates about its vertical diameter with an angular speed of `40"rad"s^(-1)` in a uniform horizontal magnetic field of magnitude `2xx10^(-2)T`. If the coil form a closed loop of resistance `8omega`, then the average power loss due to joule heating isA. `2.07xx10^(-3)W`B. `1.23xx10^(-3)W`C. `3.14xx10^(-3)W`D. `1.80xx10^(-3)W`

A circular coil of radius 6 cm and 20 turns rotates about its vertical

1.	A circular coil of radius 6 cm and 20 turns rotates about its vertical diameter with an angular speed of `40"rad"s^(-1)` in a uniform horizontal magnetic field of magnitude `2xx10^(-2)T`. If the coil form a closed loop of resistance `8omega`, then the average power loss due to joule heating isA. `2.07xx10^(-3)W`B. `1.23xx10^(-3)W`C. `3.14xx10^(-3)W`D. `1.80xx10^(-3)W`
Answer» Correct Answer - A Here, `r=6cm =6xx10^(-2)m`, `N=20,omega=40 "rad" s^(-1)` `B=2xx10^(-2)T,R=8Omega` Maximum emf induced, `epsi=NABomega` `=N(pir^(2))Bomega` `=20xxpixx(6xx10^(-2))^(2)xx2xx10^(-2)xx40=0.18V` Average value of emf induced over a full cycle `epsi_(av)-0` Mixmum, value of current in the coil, `I=(epsi)/(R)=(0.18)/(8)=0.023A` Average power dissipated, `P=(epsil)/(2)=(0.18xx0.023)/(2)=2.07xx10^)-3) W`

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