I would say vibrations, but is there choices?
Answer:
0.0222T
Explanation:
Frequency (f) =90 rev/s
Voltage = 1.15 v
Radius of coil = 1.00cm
= 0.01m
No of turns of wire (N) = 291
ω = 2πf
ω = 2π(90)
ω = 180π
A(t)= πr².sin ωt
= π(0.01)². Sin180πt
= 0.0001π.sin180πt
Differentiate A(t) with respect to t
dA/dt = 0.0001π . 180π . cos 180πt
EMF = - NB(dA/dt)
B = EMF/N(dA/dt)
B = 1.15/ -291(0.0001π . 180π . cos 180πt)
At the moment of induced voltage, cos180π = 1
B = 1.15/ -291(0.0001π . 180π . 1)
B = 1.15/ -51.7
B = 0.0222 T
The strength of the magnetic field = 0.0222T