**Problem 7: A 0.2 m wire is bent into a circular shape and is placed in a uniform magnetic field of 2 T. If the current in the wire is 20 mA, then find the maximum torque acting on the loop.**

**Solution**

**Given ** Length of the wire = L = 0.2 m B = 2 T Current = I = 20 mA = 20 * 10^{-3}A

**Required ** Torque = τ =?

**Strategy:** Since τ = IBA, where A is area of the loop. We do not know the area of the circular shape therefore, first we find it.

When the 0.2 m long wire is bent in a circular shape, the circumference of the shape will also be 0.2 m. Therefore, apply formula C = 2πr to find radius of the circle.

Now area of a circle is = πr^{2}, therefore,

Put this value (of area) in the formula for torque, given above,

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