In a circular conducting coil, when current increases from 2 A to 18 A in 0.05 sec., the induced e.m.f. is 20 V. The self inductance of the coil is
62.5 mH
6.25 mH
50 mH
None of these
|e| =Ldidt⇒20=L×(18−2)0.05⇒L=62.5 mH