phy-electromagnetism

Induced emf = -NA.(dB/dt)
where N is the no. of turns of the coil
A is the cross-sectional area
dB/dt is the rate of flux change

Given dB/dt = 4x10^-3/0.5 T/s = 8x10^-3 T/s
A = pi x 0.1^2 m^2 = 0.0314 m^2
Hence, induced emf = 100 x 0.0314 x 8x10^-3 v = 0.025 v