Answer:
The average induced emf in the coil is 20.19 mV
Step-by-step explanation:
Given;
diameter of wire, d = 8.10cm = 0.081 m
initial magnetic field strength, B₁ = 0.71 T
final magnetic field strength , B₂= 0.24 T
time = 0.12 s
According to Faraday's law, average induced emf in the coil is directly proportional to the rate of change of flux.

where;
A is the area of the wire = ¹/₄ (πd²)
= ¹/₄ (π x 0.081²) = 0.005154 m²

Therefore, the average induced emf in the coil is 20.19 mV