can someone help with these?

3. 0.0125 V
4. change in time, ∆t
3. Faraday's law says ...
[tex]\dfrac{\Delta\Phi_B}{\Delta t} \ \text{(through a fixed area) = induced emf}[/tex]
With suitable units, the magnetic flux Φ is the product of the magnetic field strength and the area of the loop. So ...
EMF = (∆B/∆t)·A = (0.250 T/s)·(0.05 m²) = 0.0125 V
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4. Refer to the discussion for problem 3. EMF is proportional to the change of flux with respect to time.