Question

Which of the following is true about magnetic dampening? Conductors experience magnetic dampening as it enters or leaves a uniform magnetic field. None of the other four statements are true about magentic dampening. Conductor is slowed as it enters the field but sped up as it exits it. Magnetic dampening is independent of the speed of the conductor. Magnetic dampening is greatest when the conductor is completely in a uniform magnetic field.

Answer 1

Magnetic damping
when a conductor enters or leaves the magnetic field induced current(motional emf associated current )will be developed in the conductor , which is called Eddy current makes the conductor damping

so the answer is

Conductors experience magnetic dampening as it enters or leaves a uniform magnetic field

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Given circular loop with radius r = 0.30 m
in a changing magnetic field , producing the induced voltage is e = 1.5 V

the change in magnetic field is dB ?

we know from Faraday's law,   Induced emf , e = -d(phi)/dt

   e = -d(B*A)/dt
  
   e = -A(dB/dt)

   e = -pi*r^2(dB/dt)

   1.5 = pi*0.3^2(dB/dt)

   dB/dt = 5.31 T/s

so the answer is 5.31 T/s