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A circular wire loop of radius R, mass m...

A circular wire loop of radius R, mass m carrying current I lies on a rough surface (as shown in Fig. 1.86). There is a horizontal magnetic field `vec B.` How large can the current I be before one edge of the loop will lift off the surface?

Text Solution

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The loop will start to lift off when the magnetic torque equals the gravitational torque as shown in Fig.
The magnetic torque acting on the loop,
`tau_m=MB=IpiR^2B`.
The gravitational torque exerted on the loop, `tau_g=mgR`.
So, `IpiR^2B=mgR implies I=(mg)/(piRB)`
.
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