A flat search coil used in a geophysical survey consists of 1200 turns of wire. The average cross-sectional area of the coil is 3.5 × 10-4 m2. During a calibration test, the magnetic flux through the plane of the coil is reduced from an initial value of 8.0×10−5 Wb8.0 \times 10^{-5}\text{ Wb}8.0×10−5 Wb to zero in a time interval ttt. This change induces an average electromotive force (e.m.f.) of 2.4 V across the ends of the coil.
What is the value of ttt?
3.3×10−5 s3.3 \times 10^{-5}\text{ s}3.3×10−5 s
0.040 s0.040\text{ s}0.040 s
25 s25\text{ s}25 s
1.4×10−5 s1.4 \times 10^{-5}\text{ s}1.4×10−5 s