2 An $N = 25$ turn circular coil of wire has diameter $d = 1.00\U{m}$.
3 It is placed with it's axis along the direction of the Earth's
4 magnetic field of $B = 50.0\U{$\mu$T}$, and then in $t = 0.200\U{s}$
5 it is flipped 180\dg. An average emf of what magnitude is generated
7 \end{problem*} % problem 23.2
10 The flux before the flip is
12 \Phi_{Bi} = AB = N \pi r^2 B \;,
14 and the flux after the flip is
16 \Phi_{Bf} = -AB = -N \pi r^2 B \;.
21 \varepsilon = - \frac{d\Phi_B}{dt} = 2 N \pi r^2 B/dt = \ans{9.82\U{mV}} \;.