Posted by Steven on .
A wire is bent into the shape of an planar Archimedean spiral which in polar coordinates is described by the equation
r=bθ.
The spiral has N=100 turns and outer radius
R=10 cm (R is the distance from point O to point T). Note that in the figure below we show a spiral having only 3 turns. The circuit is placed in a homogeneous magnetic field perpendicular to the plane of the spiral. The time dependence of the magnetic field induction is given by
B=B_0 cos (ωt)
where
B_0=1 μT and ω=2×10^6 s−1
Determine, the amplitude of the emf in Volts induced in the circuit.

Physics 
Elena,
ℰ = N•dΦ/dt = N•d(B₀Scosωt)/dt =
= NB₀Sωsinωt,
ℰ max= NB₀Sω,
Without the figure, I believe that S=πR² =>
ℰ max= NB₀πR²ω =
=100•10⁻⁶•3.14•0.1²•2•10⁶ =6.28 V